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					         ENERGY EFFICIENT ELECTRIC DRIVES
         Assoc. Prof. Svilen Rachev, PhD
         Technical University - Gabrovo



Abstract:      Аccording to the data available the electro-mechanical systems driven by electric motors
consume more than 66% of all electric energy generated in countries such as USA, Japan and European
Union.
The use of adjustable electric drives in all branches of industry makes it possible to improve the
technological processes, to ensure the overall mechanization and automation of production, to contribute
to the improvement in the quality of output, to a reduction in its prime cost, to a rise in productivity of
labor, to an increase in reliability and term of the service of equipment. Of particular importance is the
energy-saving aspect of electric drives. The insufficient knowledge referring to the specific features of the
operation of the interaction between the adjustable-speed electric drive and the motor does not allow the
improvement of the electric drive due to the modernization of the motor. The comprehensive analysis of
the electric machines in systems controlled by electric drives on the basis of a systematic approach and
methods of systems analysis will provide an opportunity to design special adjustable-speed motors with
improved regulation, starting, dynamic and vibration-acoustic indices, decreased by weight-dimensions
and costs characteristics.

Facts
Energy is not for free, as we know. Now efficiency is the focus at all power levels.
Electrical energy is an extremely valuable commodity and many market studies demonstrate that the
demand for electrical energy is continually increasing exponentially. In the period from 2001 to 2006,
energy consumption increased by 16.1% (Source: BP Statistical Review of World Energy, June 2007).
Due to the limited availability of electrical energy and ever increasing oil prices, however, a new
technical age has begun – an age in which the goal is to reduce electrical energy consumption and
promote relevant researches.
The world energy consumption is expected to increase 57% through the years 2002-2025. Regulatory
bodies worldwide have imposed efficiency standards to our field that raise the bar and challenge power
designers. In our daily lives we see, participate in, and often undertake initiatives for energy conservation.
We are able to see the fruits of our labor in the vast array of products that are available to reduce energy
consumption or include power saving features.
The global demand for electricity is growing annually between 2 and 3 percent. The Energy Information
Administration (EIA) is expecting energy demand to double to 30.1 million GWh from 2004 to 2030 -
with China and India being the main drivers of this growth in electricity.
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According to the German Electrical and Electronic Manufacturers' Association (ZVEI), if the German
industry would convert to electronically controlled drives to a level of 50 percent, electricity savings of 20
percent could be achieved. In numerical terms, this would amount to 22 TWh annually or nine coal-fired
power stations in the 400-MW class that could be saved.
The potential that this improvement would allow at global level can be seen from the fact that currently
only about 10 percent of electrical drives are estimated to be electronically controlled.
In addition, electronic controllers in electrical drive systems can yield large savings. There are two
principal approaches for drive systems which can help consume energy more efficiently.
On the one hand, there is the energy optimization of traction drive systems in combination with braking
power recovery. On the other hand, in the area of conventional electrical drives, inverter technology and
power electronics can reduce the individual consumption of such applications by up to 40 percent.
In the real world, the motor selection process can be complex and the decision must balance the ease of
control with other system-related variables such as the ease of maintenance, system response to failure,
the operating environment, thermal management and cost.
Variable speed electric motor drives can save a lot of energy. Improving motor efficiency and motor
management practices represents a golden opportunity for EU industries to increase their productivity and
profitability.
Modern control methods for three-phase motors are an essential component in today‟s machinery and
equipment. These motors‟ high efficiency and low noise level, combined with the demands for long
service life, make them the drive of choice in a range of industrial machinery and consumer goods.
Although electric motors are commonplace today, there are concerns about their rates of energy
consumtin and output. With electric motor being increasingly used, the concern about conserving energy
for environmental and practical reasons are also growing.
Electric motors are pervasive: in the office, the home, in manufacturing and in transportation. Electric
motors use 65 to 70% of the power consumed in manufacturing and 57% of all electrical consumption
worldwide [5]. If engineers feel that they should reduce energy consumption, both for economic and
environmental reasons, then this is a clearly a target area: the sums are fascinating.
It has been estimated that the average electric motor in use today is around 88% efficient in turning the
electrical energy that it consumes into mechanical energy, depending on the application conditions. For
large motor, studies indicate that this efficiency could be increased to around 96%.
Other savings could come from improved overall systems efficiency – making better use of the
mechanical energy produced by the electric motor – and from matching the electric motor more closely to
the task instead of over-specifying. The effects of these savings would be considerable, both
economically and environmentally, and this is leading both to voluntary efforts and regulatory



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requirements. To achieve these savings, there will need to be an increased use of electronic motor
controls.


Improving controls
A relatively simple fix is to electrically control the output from the motor to match the task. For example,
in an air-conditioning system, the motor driving the air pump frequently runs at a fixed speed, and the
airflow is governed by a flap that moves to let more or less air through: a similar thing can happen when
pumping a fluid. If the control knob, instead of opening or closing a flap, increases or decreases the speed
of the motor, then there may be significant power savings.

More efficient motors
There are programmes around the world – some mandatory and others voluntary – to improve the
efficiency of electric motors. These programmes tend to be based on improved quality of materials to
provide better magnetic fields, lower resistance, and lower mechanical losses. However, despite measures
to improve the efficiency of an electric motor, the latter is still intrinsically inductive and so intrinsically
inefficient. However, there are things that can be done to help attenuate the problem.

Comments on EEM penetration
Energy efficient motors (EEMs) have the following advantages:
♦ reduced breakdown of motors as a result of improved design and construction, giving many years of
valuable service beyond the initial payback period;
♦ significant savings as a result of selecting, purchasing and effectively operating the correct motor for an
application;
♦ reduced sensitivity of the power factor and efficiency to voltage and load fluctuations;
♦ power use in motors; the total power consumed by a motor consists of the power used for driving the
load and power lost as heat.
New efficient motors bring tough difficulties to the designers because they have to add about 25 to 30 %
materials inside the motors for getting the new improved efficiencies for induction motors (IM), at the
same time preserving the old correlation between height of shaft and range of powers. Usually the motors
will be longer and the transversal structure of inner part of the machine will suffer important
modifications.
An example of the benefits of using EEM is taken from the literature. There is significant potential for
productivity increases, reduced energy costs (the most significant advantage) and environmental benefits.
An average electric motor uses 50 times its initial cost in electrical energy over a 10–15 year life. A
€1000 motor will use €50 000 of energy over a 10–15 year period. Saving 10% on the purchase price of a


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€1000 standard motor saves €100. Nevertheless, spending €1250 on a motor that is 5% more efficient
saves 5% of €50 000, or €2500.
In the last 20 years research and development into improving motor construction and manufacturing
techniques led to improvements in full-load efficiencies of 2.5% (that is, a 10kW energy efficient motor is
typically 3% more efficient). Thorough design and monitoring of the distribution system will enable the
EEM to operate at optimum efficiency.

Opportunities for Energy Savings with High-Efficiency Electric Motors
The use of motors in the residential sector is quite diverse. Motors range from the smaller motors in the
0.4 to 0.8 kW range typically used in equipment such as refrigerator/freezer compressors, central a/c
condenser fans, clothes washers and dishwasher pumps to the 3.0 to 7.5 kW motors typically used in
equipment such as central a/c compressors and heat pump compressors. The smallest motors in the < 0.2
kW range are typically used in equipment such as clothes dryer drum rotation and convection oven
rotation motors [1].

Energy-Saving Technology
From [1] it is evident that significant energy-saving opportunities exist in several areas. Among the most
promising:
♦ Variable-speed compressors/variable-speed fans for home refrigerators;
♦ Variable-capacity compressors/variable-speed indoor blowers for residential furnace fans and small
commercial air conditioning;
♦ Efficient evaporator fans in commercial refrigeration equipment;
♦ Variable-speed blowers in commercial space conditioning air-handling equipment;
♦ Reduction of parasitic and other losses in commercial building thermal distribution systems_hydronic
circulating pumps, cooling water pumps, and heat rejection fans, as well as conditioned air handling.

Market Barriers
Achieving savings potential will require addressing significant market barriers. The motor and variable-
speed drive markets have numerous stakeholders with many different, sometimes conflicting, interests.
Interested parties include building occupants, motor and drive manufacturers, OEMs, appliance
manufacturers, equipment distributors, trade associations, electric utilities, certification organizations,
research centers, government agencies, engineering firms and construction companies.

One of the main issues influencing the acceptance of variable speed drives (VSDs) in the design phase of
commercial building is the lack of trained and experienced consulting engineers with the knowledge
necessary to design these systems.


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There are many opportunities for energy savings in the residential and commercial sectors using high-
efficiency electric motors. Many applications are already promising in terms of costs, availability,
efficiency, and energy-savings benefits. However, some of the more efficient of the identified
technologies are commercially available, but lack the critical production level necessary to be
economically viable.
Because new technologies often involve a relatively high risk-to-reward ratio for manufacturers, market
forces alone may not ensure that these technologies will be available to end-users. In many areas there is a
clear role for government. For example, governmental initiatives could include the following [1]:
♦ Governments could provide assistance to private industry, universities, or non-government agencies that
undertake motor research activities, to encourage the development of new motor technologies;
♦ Working with motor manufacturers, governments could urge OEMs to integrate efficient motors and
VSD technology in their HVAC or refrigeration products;
♦ Governments could endorse training initiatives for small motors and their application, in partnership
with trade associations.
These are but a few of the potential measures open to governments and motor-efficiency stakeholders.
The findings and detailed analysis in this study will be helpful in support of motor manufacturers,
equipment manufacturers, distributors, and other participants in the motor industry.

Current Research in Electric Motors for Commercial Applications
Various groups undertake research in motors for residential and commercial applications. Motor
manufacturers do their own research, contract research to private firms, and support industry consortia
and university research programs. Government also supports cooperative research efforts and individual
programs, but to a lesser extent. Additionally, a great deal of research from other fields has applications to
motor technology.
Research topics vary across research groups, but there are a few common drivers. First, induction motors
are technically mature. Research expenditures therefore face diminishing returns. There are also added
incentives for new technologies to capture market share from a mature technology. Second, substantial
advances in other fields are expanding the potential applications for stepper motors and variable-speed
control of induction motors. These include digital signal processing (DSP), power electronics, magnetic
materials, and mathematical modeling. Applying these advances to motor technology has potentially high
returns and is attracting a great deal of research activity.
Since induction motor technology is mature, most research focuses on reducing costs and increasing
productivity rather than improving performance. Computer models to assist motor designers, new
winding methods, and new steels are examples of typical research topics. Most motor manufacturers
conduct this research internally, or contract out under proprietary arrangements.


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Variable-speed control of induction motors is one area that continues to attract a great deal of research
effort. Although also considered technically mature by virtue of their history in industrial process control,
there is a large potential market in smaller industrial motors, and in fans, compressors, and appliance
motors in the residential and commercial sectors. Furthermore, given the dominance of induction motors,
there are retrofit opportunities. Since traditional methods of modulating induction motor speed or varying
process rates can be extremely energy inefficient, end users have a financial incentive to switch to
variable-speed drives. The attractive market draws private funding devoted to reducing costs and size and
expanding applications. Universities and consortia are also researching ways to ameliorate the harmful
effects of drive harmonics on power grids.
Note that there are many design options for improving the system efficiency besides improving the motor
efficiency or using variable-speed drives for efficient part load operation. Obvious examples include
increased insulation, larger heat exchangers, adaptive defrost, etc. An inherent advantage of the efficiency
standard setting process is that once a standard level is set, manufacturers are free to develop the most
cost-effective design to meet the standard. Thus, motor efficiency increases are only part of the potential
for efficiency improvement in these types of appliances. This observation is consistent with other
published studies of the potential for reduced energy consumption by motor driven equipment.
Incremental, motor efficiency improvements generally account for only 10 to 20 percent of the estimated
potential energy savings. The majority of these savings come from equipment, product, or process
redesign. The use of adjustable-speed drives, which often requires a redesign for the driven process,
typically involves a much larger scope of activity than incrementally increasing the motor efficiency.

Study on centrifugal-type loads
The value of adjustable speed control in industrial applications is well proven by the increasing number of
installations in which induction motors are powered by VSDs. Adjustable speed drives can provide
energy savings and improve process control. This is especially true for systems such as fans and pumps
where flow control is achieved by baffles and valves. However, VSDs have drawbacks including: high
purchase and installation costs, motor bearing pitting, insulation failure, electromagnetic interference with
control and measurement equipment, harmonic distortion generation, and tripping due to power
disturbances. The correction of these problems requires additional equipment and techniques which
further increase the capital cost [2].
The study [2] has focused on centrifugal-type loads where the torque decreases rapidly with speed.
Recent surveys indicate that fans/blowers and pumps comprise 42% of all industrial loads by energy
consumption. The traditional means of regulating the flow from these loads, respectively by throttling
valves for pumps and baffling vanes for fans, are well known to be inefficient. The wasted energy is
dissipated as heat in the throttling systems and the fluids being circulated in the industrial processes. Over


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the past 20 years, power electronic adjustable-speed, or VSDs have been introduced in increasing
numbers to provide a high-efficiency alternative means of control by matching the output torque and
speed of induction motors to the requirements of the loads. However, the energy savings resulting from
the introduction of VSDs are obtained at the cost of significant capital expenditure: VSDs are generally
much more expensive than the induction motors they control, and the cost of installation and
environmental provisions for the VSD, must be factored into the overall cost/benefit equations. For
example, the average cost for 100kVA VSDs is about €4920 (€49/kVA), for 50kVA drives is about
€2895 (€58/kVA), and motors in this range run about €21/kW for industrial totally enclosed fan cooled
motors, and €16/kW for drip proof motors for office/commercial installations. In Europe and Japan,
where energy costs are substantially higher than in the USA, VSDs have been installed in far greater
percentage numbers. According to studies conducted the VSD market penetration (i.e. the percentage of
motors being driven by VSDs) in the USA is 18% in currently sold systems and 12% in existing
installations, in Europe 24% sold and 19% installed and finally in Japan 45% sold and 38% installed.
In addition to their relatively high capital cost, VSDs have experienced technical impediments to their
introduction and adoption by industry. Early model of VSDs suffered reliability problems. These forced
plant designers/operators to retain the throttles/baffles and to install VSD by-pass switches to ensure
uninterrupted processes. This compounded the capital and installation payback problem. Advances in
power electronic devices have helped reduce the reliability issues of VSDs. Thyristors and bipolar
junction transistors (BJT) have been replaced by insulated gate bipolar transistors (IGBT) and power
MOSFETs. These advanced devices have reduced VSD circuit complexity and have improved the
performance by use of higher device switching speeds. The latter benefit for the VSD has, in certain
cases, produced operational problems in the induction motors. These problems include: increased stress of
motor insulation, especially for smaller motors connected via long cable lengths; common-mode voltage
effects leading to capacitively induced motor shaft voltages and resulting bearing currents; both radiated
and conducted electromagnetic interference (EMI); high harmonic content of the currents drawn from the
supply, particularly at low load levels.
Effective solutions have been developed to all of those problems, but these solutions generally require
additional equipment, thus increasing the complexity and cost of the system.




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      Fig. 1. Alternative Methods of Fluid Flow Control: a) Throttling; b) Motor Speed Adjustment




                  Fig. 2. Power Factor Comparisons for Control by Throttling and VFD

Pumping systems account for nearly 20% of the world‟s energy used by electric motors and 25% to 50%
of the total electrical energy usage in certain industrial facilities [3]. Significant opportunities exist to
reduce pumping system energy consumption through smart design, retrofitting, and operating practices. In
particular, the many pumping applications with variable-duty requirements offer great potential for
savings. The savings often go well beyond energy, and may include improved performance, improved
reliability, and reduced life cycle costs – Figure 3. Most existing systems requiring flow control make use
of bypass lines, throttling valves, or pump speed adjustments. The most efficient of these is pump speed
control. When a pump‟s speed is reduced, less energy is imparted to the fluid and less energy needs to be
throttled or bypassed.




      Fig. 3. Typical life cycle cost LCC components for a mediumsized industrial pumping system




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Benefits of VSDs
VSDs offer several benefits, some of which are relatively easy to quantify, and others of which are less
tangible, but there are some potential drawbacks, which must be avoided.
Energy Savings
With rotodynamic pump installations, savings of between 30% and 50% have been achieved in many
installations by installing VSDs. Where positive displacement pumps are used, energy consumption tends
to be directly proportional to the volume pumped and savings are readily quantified.
Improved Process Control
By matching pump output flow or pressure directly to the process requirements, small variations can be
corrected more rapidly by a VSD than by other control forms, which improves process performance.
There is less likelihood of flow or pressure surges when the control device provides rates of change,
which are virtually infinitely variable.
Improved System Reliability
Any reduction in speed achieved by using a VSD has major benefits in reducing pump wear, particularly
in bearings and seals. Furthermore, by using reliability indices, the additional time periods between
maintenance or breakdowns can be accurately computed.

Potential Drawbacks of VSDs
VSDs also have some potential drawbacks, which can be avoided with appropriate design and application
[3].
Structural Resonance
Resonance conditions can cause excessive vibration levels, which in turn are potentially harmful to
equipment and environment. Pumps, their support structure, and piping are subject to a variety of
potential structural vibration problems (resonance conditions). Fixed-speed applications often miss these
potential resonance situations because the common excitation harmonics due to running speed, vane
passing frequency, plunger frequency, etc., do not coincide with the structural natural frequencies. For
VSD applications, the excitation frequencies become variable and the likelihood of encountering a
resonance condition within the continuous operating speed range is greatly increased. Pump vibration
problems typically occur with bearing housings and the support structure (baseplate for horizontal
applications, motor and stool for vertical applications).
Pressure pulsations are the common excitation mechanism. These pressure pulsations may be further
amplified by acoustic resonance within the pump or the adjacent piping.
Rotor Dynamics
The risk of the rotating element encountering a lateral critical speed increases with the application of a
VSD. Lateral critical speeds occur when running speed excitation coincides with one of the rotor‟s lateral


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natural frequencies. The resulting rotor vibration may be acceptable or excessive, depending on the modal
damping associated with the corresponding mode. Additionally, drive-induced torque harmonics may
cause resonance conditions with torsional rotor dynamic modes. However, such conditions are usually
correctible or preventable. Variable speed vertical pumps are more likely than horizontal machines to
exhibit operational zones of excessive vibration. This is because such pumps‟ lower natural frequencies
are more likely to coincide with running speed. Small, vertical closecoupled and multistage pumps
normally do not present this type of problem.
Additional Considerations for VSDs
The introduction of VSDs requires additional design and application considerations. VSDs can be fitted to
most existing motors in Europe and other areas, which use a 400 Volt (V) network. However, this is
generally not the case in the United States, and other areas where network voltages exceed 440 V. Hence,
reinforced insulation “inverter duty” motors are often needed. The high rate of switching in the PWM
waveform can occasionally lead to problems.
For example:
• The rate of the wavefront rise can cause electromagnetic disturbances, requiring adequate electrical
screening (screened output cables). Filters in the inverter output can eliminate this problem.
• Older motor insulation systems may deteriorate more rapidly due to the rapid rate of voltage change.
Again, filters will eliminate this problem.
• Long cable runs can cause “transmission line” effects, and cause raised voltages at the motor terminals.
Voltages can be induced in the shafts of larger motors, potentially leading to circulating currents, which
can destroy bearings. The following corrective measures are required:
• Insulated non-drive-end bearings are recommended on all motors over 100 kilowatt (kW) output rating.
• Common mode filters may additionally be required for higher powers and voltages.
The converter will have losses, and ventilation requirements for the electronics can be an important issue.
The life expectancy of the converter is generally directly related to the temperature of the internal
components, especially capacitors.
The converter may require installation in a less onerous environment than the motor control gear it
replaces. Specifically:
• Electronics are less able to cope with corrosive and damp locations than conventional starters.
• Operating a VSD in a potentially explosive atmosphere is not usually possible.


The “technology status” entries are defined as:
♦ Current: Technologies that are currently in use but have not achieved broad market penetration;
♦ New: Technologies that are commercially-available but presently not used in commercial building
HVAC equipment and systems;

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♦ Advanced: Technologies yet to be commercialized or demonstrated and which require research and
development.


Several factors characterize the most promising areas for the application of the 15 technology options,
and HVAC energy-efficiencies in general. First, the economics of energy-efficient equipment improve in
regions with high electricity and gas rates. For cooling and ventilation technologies, higher demand
charges can also result in shorter simple payback periods. Second, packaged rooftop equipment presents
several opportunities for more cost-effective efficiency gains due to the lower efficiency equipment
typically employed. Third, institutional purchasers (governments, hospitals, educational establishments,
etc.) tend to have a longer time horizon than most commercial enterprises, reducing their sensitivity to
first-cost premium and making HVAC technologies with reasonable payback periods more attractive.
Fourth, in many instances hospitals should be a preferred building type for more efficient equipment and
systems, as they consume high levels of HVAC energy because of „round the clock operations and high
requirements, and are often long-standing institutions willing to invest more funds up front provided they
reap a solid return over the equipment lifetime.
Energy use for heating and cooling has long been a target for reduction efforts. In fact, significant
efficiency improvements have been achieved over the years in these efforts. For example, the efficiency
of a typical centrifugal chiller has increased 34% over the past 20 years. Energy use reductions have been
achieved by the efforts of a wide range of players in the market, including manufacturers, contractors,
specifying engineers, and government laboratories and agencies. In spite of these efforts, energy use for
space conditioning remains a very large portion of the total national energy use picture and still provides
significant opportunity for energy use reduction.
On the other hand, historically, several factors have hindered energy efficiency gains. For most
businesses, energy is not a core part of the business. Consequently, many businesses are unwilling to
make substantial investments in energy efficiency improvements that would displace core capital
investments or potentially disrupt core functions, even if the energy efficiency improvements have very
favorable return-on-investment characteristics. Tax codes effectively pose a barrier to energy savings in
companies, as energy expenses are deductible business expenses, while energy investments count against
capital. Similarly, budget structures can impede energy-efficiency investments, even with acceptable
payback structures, because a facility may have distinct construction and operating budgets that are not
fungible. Corporate billing methods often work against energy efficiency investments as well by not
directly billing entities for energy expenses. For instance, most firms do not keep track of energy costs as
a line item for each cost center and many companies, most notably chains/franchises, do not even see
energy bills as they are handled and paid at a remote location.



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When new buildings are built or major renovations undertaken, contracting practices often impede the use
of energy efficiency in new construction. To save time and cost and avoid the potential risk of different
HVAC system designs, design firms may simply copy old designs and specifications that worked in the
past, preventing consideration of more efficient system designs and/or equipment options. Finally, energy
costs simply do not represent a significant portion of expenditures for most buildings, e.g., one study
found that energy expenditures account for just over 1% of total annual expenditures for a mediumsized
office building, with HVAC expenses on the order of 0.5%.
In many instances, the simple payback period, SPP, was used to quantify the economics of a technology.
It equals the cost of the energy savings afforded by the technology, CEsave, divided by the incremental
premium of the energy efficiency measure, which is the difference between the cost of the default
technology, Cdef, and that of the technology option, Copt, [3]:
           C Esave
SPP                  .
        C def  C opt


IDENTIFIED POTENTIAL SAVINGS
This section presents the identified potential electricity savings in the surveyed industrial sectors and in
the tertiary sector, which can be achieved by the application of energy efficient motors and electronic
variable speed drives [4]. Studies show that the electricity savings potential would be much larger if other
motor system improvements were considered, namely, good design of the motor system, high efficiency
end-use devices (pumps, fans, etc.), efficient transmission, good quality repair, improved maintenance,
improved power quality, correcting motor oversizing, etc. However, it is difficult to accurately quantify
these potential savings with accuracy, and the estimates of electricity savings potential, which are drawn
for the industrial and for the tertiary sectors, are therefore very conservative. For example, a recent study
estimated that the potential for energy savings in the EU from better quality repair of motors is around 8
TWh pa.

Methodology
In order to estimate the electricity savings potential, a time horizon of 2015 was used. According to
“European Energy to 2020”, in the “conventional wisdom” scenario, the annual average growth rates of
the electricity consumption up to 2015, in the industrial and tertiary sectors are estimated to be 1.2% and
1%, respectively. Table 1 shows the estimated motor electricity consumption in the industrial and tertiary
sector, by power range in 2015, assuming frozen efficiencies for induction motors [4].




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Technical Potential
The technical potential represents the energy savings that can be achieved applying the Energy Efficient
Motors and Variable Speed Drives to all the available opportunities, irrespective of the cost-effectiveness
of the measure.
Economic Potential
The economic savings potential represents the energy savings that can be achieved when the efficient
technologies are only applied to cost effective applications.
One of most sensitive factors for the cost effectiveness of EEMs and VSDs is the number of operating
hours. Cost-effectiveness analysis in this study has been based on the cost of saved energy. The input data
for the cost benefit analysis was the field survey. The CSE was determined according to the equation:




The cost of implementation includes the cost of the equipment, plus the cost of installation and the
interest rate is considered to be 10%.
When the CSE is less than the typical average price of electricity in the industrial and in the tertiary
sectors (which was considered 0.055 €/kWh and 0.1 €/kWh respectively), it is costeffective to apply the
measures under consideration. It is cost effective to introduce EEMs in all power ranges in the analysed
sectors. In what concerns VSDs, there are some situations in which the introduction of variable speed
control is not attractive, especially in the lower power ranges.

  Table 1: Estimation of motor electricity consumption by power range, by 2015 based on the average
         growth rates, assuming 1.2% and 1% growth rates in the industrial and in the tertiary
                                          sectors, respectively.
               Motor electricity consumption forecast by 2015 [TWh]
               Power Ranges        Industrial sector      Tertiary sector
             [0÷0.75]                       6.2                   14.2
             [0.75÷4.00]                   46.2                   66.2
             [4.00÷10.00]                  55.8                   58.8
             [10.00÷30.00]                 95.0                   53.6
             [30.00÷70.00]                143.9                   12.7
             [70.00÷130.00]                83.6                   10.7
             [130.00÷500.00]              166.3                    6.3
             [500.00÷---]                 123.5                    1.8
             Total [TWh]                  721.3                  224.2

REPAIR DECISIONS
In the past little consideration has been given to the impact of rewinding methods on motor efficiency. It
is generally accepted that it is cheaper to repair failed motors above 5 kW than to replace them. When a
motor fails, the main concern of most motor users and rewinders is to get the motor back into service as


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quickly and inexpensively as possible. This situation sometimes leads to the use of repair processes,
which can significantly reduce the efficiency of the motor. However, the increasing awareness of the huge
amount of electricity consumed by electric motors, coupled with the increasing focus on Energy-
Efficiency and the emergence of Energy-Efficient Motors, has highlighted the effects that motor repair
can have on efficiency.
Laboratory testing studies confirm that motor repair practices reduce motor efficiency typically between
0.5 and 1%, and sometimes up to 4%. This is because the rewinding processes are in general not as well
controlled as the original design and production of the motors. Additionally, some rewind shops do not
have the equipment or the information necessary to repair every type of motor to the manufacturers´
specifications.
Most users ignore or do not know what happens during the repair process, nor do they do not worry about
the possible efficiency drop after the repair. They are usually unaware of the impact on the energy bill due
to reduced efficiency levels of electric motors, after repair. It is known that the motor repair market,
represents approximately 3 times the new motor market.
This is why the improvement of the repair market is so important in order to decrease the operating costs
of motor users.

Energy Efficient Motors
Energy Efficient Motors (EEMs), have higher efficiency values which usually are in the range 2-6
percentage points higher than conventional motors. Typically they can cost 20%-30% more than Standard
Motors, although some manufacturers are now offering EEMs at lower or even zero price premiums.
EEMs have lower losses than standard efficiency motors which normally lead to a lower operating
temperature and to longer lifetime. Therefore, they can also reduce maintenance costs as well as energy
bills.

Table 2: Economics of EEM or standard motor purchase/repair scenarios for a 45 kW, 1500 rpm motor.
      Scenario         Estimated      Average        Average      Savings per       Simple
                       Efficiency   New Motor         Cost of         Year         Payback
                       Difference      Price          Repair
                      %                  €               €               €             €
Purchase EEM          4.00             1848             968            375            2.3
versus poor repair
Purchase Standard     1.00             1478             968             97            5.3
versus poor repair
Purchase EEM          3.25             1848             968            302            2.9
versus good repair
Purchase Standard     0.25             1478             968             24           21.3
versus goor repair
                   Assumptions: 4000 hours/year; 0.06 €/kWh; load factor = 0.75



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Finally, it can be said that the main factors to decide whether to replace an old damaged motor by an
EEM or to repair the damaged motor are:
♦ Type of damage suffered by the motor, namely in terms of allowing a good repair;
♦ Actual Efficiency of the motor or the estimated Efficiency after repair (Based on the repair methods);
♦ Efficiency of new EEM;
♦ New motor price;
♦ Repair price;
♦ Operating hours per year and load factor;
♦ Energy price;
♦ Financial incentives;

Table 3 summarises the estimated technical and economic savings potential in the industrial and in the
tertiary sector with the application of EEMs and VSDs by 2015. The large scale application of VSDs can
lead to the achievement of a huge electricity savings (96TWh). The wide application of EEMs, although
its impact is not so impressive as VSDs, still leads to substantial electricity savings (36TWh). If we
assume average costs of 0.055€/kWh and 0.1€/kWh in the industrial and in the tertiary sector,
respectively, the electricity savings would translate into 5 900 M€ per year.

                            Table 3: Potential Electricity savings in the year 2015.
                                                EEMs                  VSDs           EEMs+VSDs
                            Industry              24.1                 71.0             92.4
     Technical
                            Tertiary              11.5                 24.6             34.7
     Potential
                          Total [TWh]             35.6                 95.6            127.1
                            Industry              24.1                 44.9             67.3
     Economic
                            Tertiary              11.5                 11.4             22.2
     Potential
                          Total [TWh]             35.6                 56.3             89.5

Cost-effectiveness analysis, based on the Cost of Saved Energy, showed that the application of Energy
Efficient Motors in Industry and in the Tertiary sector is cost-effective in the vast majority of cases.
Therefore, the economic potential is roughly equal to its technical potential, which amounts to 24 TWh in
industry and to 11.5 TWh in the tertiary sector. When considering Variable Speed Drives, there are
situations, especially in the lower power ranges, in which the application of speed control is not cost-
effective. In the industrial sector, the proportion of applications in which VSDs are cost-effective is larger
than in the tertiary sector, where the number of operating hours is significantly less. The higher cost of
electricity in the tertiary sector partially compensates the reduction in operating hours.
While the savings potential available in industry are concentrated in large motors, the savings potential
available in the tertiary sector are concentrated in small motors (below 30kW), due to their relative
importance in the use of electricity. Little attention has been taken with those motors. However, motors in


                                                                                                           15
the power range [04kW] are responsible for 50% of the identified potential savings with Energy
Efficient Motors in the tertiary sector. This is due to the larger efficiency difference between standard
motors and EEMs in this power range.
In addition to these savings, further reduction in electricity consumption could result from other
efficiency improvements, which have not been quantified in this study, such as good design of the motor
system, high efficiency end-use devices (pumps, fans, etc.), efficient transmission, good quality repair,
improved maintenance, proper electric supply, correcting motor oversizing, etc.
One major finding of the field characterisation was that most motors, especially small motors, both in
industry and in the tertiary sector are oversized. The replacement of those motors when they fail with
smaller motors would bring significant electricity savings. Those savings would be much higher if the
motors were replaced with energy-efficient models.
While in industry decision makers are usually aware of the possibilities for efficient improvements in the
plant, in the tertiary sector the situation is quite different. In this sector, a high proportion of buildings are
leased, not owned. Therefore there is little incentive for the landlord or tenant to spend money on energy
saving equipment. Additionally, there are some measures related to human behaviour (specially in the
tertiary sector), which could bring significant benefits in terms of electricity consumption.
Concerning EEMs more effort is needed to increase the user awareness and convince them about the real
advantages of EEMs, especially in the situation of failure, replacing the failed motor with an EEM rather
than repairing it.
Concerning VSDs, the situation is quite different. The high initial cost of a VSD, especially in the lower
power ranges, can make the application of VSDs not so cost-effective. Therefore there is a need for
further effort in this area in order to drop the price per kW of VSDs. Voluntary agreements with VSD and
OEM manufacturers could also be an effective way of promoting VSDs and improving their penetration
into the market.
Research and Development is also needed to bring to the market new energy efficient technologies, such
as integrated motors and VSDs, at a competitive price.

VSDs for Electric Motor Systems
Electric motor systems are by far the most important type of load in industry, in the EU, using about 70%
of the consumed electricity. In the tertiary sector although not so relevant, electric motor systems use one
third of the consumed electricity. It is their wide use that makes motors particularly attractive for the
application of efficiency improvements [4].
The loads in which the use of speed controls in electric drives can bring the largest energy savings are the
fluid handling applications (pumps, compressors and fans) with variable flow requirements. Other
applications which can benefit from the application of VSDs include conveyors, machine tools, lifts,


                                                                                                               16
centrifugal machines, etc. The dominant speed control technology – electronic VSDs coupled with
alternating current (AC) 3-phase motors (induction or synchronous) – have practically replaced other
technological solutions: mechanical, hydraulic as well as direct current (DC) motors.
For the assessment of electricity savings potential with the application of VSDs, three different scenarios
have been considered: the technical savings potential, economic savings potential assuming constant VSD
prices, and the economic savings potential assuming a VSD price decrease of 5% per year.


                Table 4: Estimated total electricity savings potential in TWh pa, by 2015.




   Fig. 4. Two pumping systems with same output: (a) Conventional system (Total Efficiency = 31%);
    (b) Energy-efficient pumping system combining efficient technologies (Total Efficiency = 72%).

Cost-Effective Variable-Speed Motor Control
Using sophisticated power concepts based on optimized microcontrollers provide enormous energy
saving potentials in various applications. Both improved energy efficiency and reduced system costs are
the driving factors in modern motor control designs used in fans, pumps, compressors, geared motors.


                                                                                                        17
The usage of brushless DC motors (BLDC), permanent magnet synchronous motors (PMSM) or AC
induction motors combined with powerful motor control algorithms running on optimized
microcontrollers offer the most energy efficient solutions [6].
The need of higher efficient motor drives and power conversion solutions results in an increasing demand
of related microcontrollers.
The turbulent and steadily increasing price of energy, combined with increasing government levies on
resource usage, is sharpening homeowners‟ focus on appliance energy efficiency.
Appliances such as washing machines from fixed-speed motor operation to more flexible variable-speed
operation can save energy while enabling design techniques such as advanced wash programs that also
reduce water usage. Washing machine designers have identified the PMSM as the most cost-effective and
easily controlled choice for variable-speed motor operation. Speed and torque control are much easier to
establish than with traditional induction motors, and the PMSM typically delivers greater efficiency in
terms of torque per amp. This enables a smaller motor, thereby reducing per-unit costs and simplifying
electrical and mechanical design.
A barrier to the arrival of the next-generation, ultra-efficient washer, however, is the need to implement
additional sensing components such as Hall Effect sensors, to generate rotor positional information.
Alternatively, the software challenges associated with coding a sensorless motor control algorithm
introduce large risks to the project and require specialist DSP or RISC programming skills.
Designers can overcome this barrier with a sensorless motor control algorithm in hardware tailored to
meet specific system requirements. This approach allows designers to implement variable-speed motor
drives quickly and cost effectively. Among other important benefits, executing the algorithm at a higher
speed in dedicated hardware results in better speed and torque control compared to a softwarebased
approach. This provides greater flexibility for washer designers to create efficient programs that use less
electrical energy.

The latest motion-control semiconductor technologies help designers rapidly implement intelligent-
pump controls [6].
Variable-speed intelligent pumps are rapidly gaining favour in applications as diverse as chemical
processing and building services. The growing demand for these pumps is largely due to efficiency
improvements over conventional fixed-speed „on/off‟ designs. Companies find that using intelligent
pumps to improve efficiency helps them comply with environmental legislation and also leads to
operating-cost reductions.
Traditional fixed-speed pumps always work at full capacity. Variable-speed systems match pump speed
to demand. The pumpdrive circuitry need only supply the power necessary to satisfy the system‟s
instantaneous demands. Designers can choose smaller, lighter, less expensive pumps while customers


                                                                                                        18
benefit from the fact that a pump that operates most often at a fraction of its full capacity is inherently
more reliable.
Water and wastewater management and building automation are typical target applications for intelligent
pumps. They are sensitive to operating costs and are commonly subject to Governmental control.
Intelligent pumps can contribute most in systems with widely fluctuating fluid demand or narrow-ranging
pressure requirements over a wide range of flow rates. An example is the system supplying chilled water
in an office building‟s heating and cooling system. Estimates suggest that a variable-speed pump can
reduce energy consumption in such systems by 30 to 70% (ARC Advisory Group Intelligent Pump
Market Analysis). In these applications, however, energy efficiency and cost of ownership tell only a part
of the story. Just as important is the need to keep acoustic noise as low as possible. Moreover, such
applications often require fast response times and high control accuracy to accommodate the full range of
flow requirements and to quickly match supply with demand. All of this increases the complexity of
controlling the motors at the heart of intelligent-pumping designs.
Using a digital signal controller (DSC) for field-oriented control (FOC) allows DC control techniques to
be used to improve the performance of AC induction motors. FOC controls the amplitude, frequency and
phase of the voltage vector to produce the desired amplitude, frequency and phase of the motor currents,
and offers the best efficiency and dynamic response from an AC induction motors [6].

To achieve energy efficiency, we can apply frequency-current control of AC drives, characterized by
using of autonomous current inverters (ACIs). ACIs are used to generate frequency-variable motor
current. The current regulator feeding the inverter is often built on a controllable rectifier. Compared to
voltage inverters ACIs are more easily implemented because of a reverse diode bridge missing. One of
the main features of the ACIs is the grid recuperation they can implement. Therefore, they are widely
spread today due to their high energy efficiency. The control rectifier in the closed loops switches
automatically to an inverter mode, implementing grid recuperation.

Inverters are increasingly used in motor control systems in order to improve efficiency and controllability
of the system. Inverters are used for white goods such as air-conditioners and industrial motors. The
inverter system involves higher harmonic current. So in the inverter system, a function to reduce the
higher harmonic current is needed.
In recent years, high harmonic currents generated in electric power systems are restricted in all electronic
equipment. Especially in the EU where IEC61000-3-2 is applied, the high harmonic current regulation are
severe, and the application of PFC (Power Factor Correction) is advanced.
Another aspect directly related to Efficient Electric Drives is the so called servo drives. The term comes
from the Latin word "servus" which means "servant". Initially, servo drives were mainly used as
secondary drives. However, today, they are successfully introduced as primary drives and can be

                                                                                                         19
produced with servo boosters or inverters, which makes them commonly applicable. Engineering sciences
consider the term "servo drive" as a system built on driving, transforming, gearing and controlling
devices, which purpose is to drive and control the equipment actuators.
Recently the development of electronics, material science and metal-working technologies has lead to
considerable changes in the world of driving technologies. Servo technologies were developed on the
basis of DC electric motors for years. At that time the AC motors had worse mechanical characteristics in
relation to speed regulation. With the development of electronics, in particular microcontrollers, the
control systems developed have begun to compensate these drawbacks. As a result the driving systems
have shifted from DC to AC technologies.
Servo motors are electric motors intended for driving control devices. Usually they are of small size and
power. There are also some other significant characteristicts of theirs such as mass, motor dynamics,
motion steadiness and efficiency.
Servo motors are widely used in industry, e.g. metallurgy, automotive industry, robotics, metal-working,
astronautics, aircraft industry, etc.
Both AC and DC electric motors are used in servo motors. However, they must have speed sensors and
position sensors, which distinguish them from other motor types. In addition, they are characterized by a
minimal start and stop time. This means an immediate reach of the rpm set by the electronic control, as
well as an immediate termination of the action. As an example of this extremely precise performance of
the motion set, we can take a ball-screw pair in CNC metal-cutting machines, where the cutting tolerance
accuracy could be up to 1μm.
There are three main types of electric servo motors widely used in industry today:
       squirrel cage induction motors;
       block commutation brushless DC motors;
       synchronous sinusoidal commutation brushless AC motors.

The China Motor Systems Energy Conservation Program: A Major National Initiative to Reduce
Motor System Energy Use in China
Electric motor systems are widely used in China to power fans, pumps, blowers, air compressors,
refrigeration compressors, conveyers, machinery, and many other types of equipment. Overall, electric
motor systems consume more than 600 billion kWh annually, accounting for more than 50% of China‟s
electricity use. There are large opportunities to improve the efficiency of motor systems. Electric motors
in China are approximately 2-4% less efficient on average than motors in the US and Canada. Fans and
pumps in China are approximately 3-5% less efficient than in developed countries. Even more
importantly, motors, fans, pumps, air compressors and other motor-driven equipment are frequently
applied with little attention to system efficiency. More optimized design, including appropriate sizing and


                                                                                                        20
use of speed control strategies, can reduce energy use by 20% or more in many applications.
Unfortunately, few Chinese enterprises use or even know about these energy-saving practices.
Opportunities for motor system improvements are probably greater in China than in the US.
In order to begin capturing these savings, China is establishing a China Motor Systems Energy
Conservation Program. Elements of this program include work to develop minimum efficiency standards
for motors, a voluntary “green motor” labeling program for high-efficiency motors, efforts to develop and
promote motor system management guidelines, and a training, technical assistance and financing program
to promote optimization of key motor systems [7].

The Situation in China
In 1998, China consumed 1159 billion kWh of electricity (SSB 2000), which is about 36% of U.S.
consumption (EIA 2000a), and ahead of all other countries (EIA 2000b). Of this figure, about 60% was
consumed by motors, split roughly evenly between fans/pumps and other equipment. The installed
capacity of electric motors in China exceeds 450,000 MW (CECIDC 2000).
In the following sections, we briefly describe the Chinese market for motors, including the market for
motors, motor-driven equipment (e.g., fans, pumps and compressors), speed control equipment, and
motor system design services. Following this, we briefly summarize the many opportunities to improve
motor system efficiency in China, the barriers that hinder capture of these opportunities, and discuss
current programs and policies that are designed to overcome these barriers. This information is intended
to provide context for a discussion later in this paper on a planned national program to improve motor
system efficiency in China.

China’s Motor Market
Motors. In China, most factories operate on 380 V, 50Hz electricity, and most motors follow the IEC
design parameters, the same parameters that are widely used in Europe. In China today, there are
presently three series of motors in widespread use – the JO series (originally developed in the 1950s in
Russia and redesigned in China in the 1970s), the Y series (designed in China in the 1980s), and the Y2
series (developed in China in the early 1990s). In general, the newer series of motors have better
optimized designs and use less material. However, while the newer series are better optimized, much of
this optimization has been used to reduce materials – as shown in Table 5 below, efficiency
improvements from series to series are generally either small or non-existent. Under government
regulations, the production of JO series motors has been banned since 1984, but these motors are still in
place in many factories and now account for about one-third of the installed motor stock. Approximately
95% of motor sales in China are now of the Y series, with the Y2 series accounting for about 5%. In
addition, a higher efficiency Y2e series has recently been introduced but currently is a special order item
produced by just a few manufacturers. Table 5 summarizes the relative efficiencies of these different

                                                                                                        21
types of motors (these efficiencies are generally tested according to the IEC test procedure; relative to the
IEEE 112-B test procedure used in the US, the IEC procedure generally results in a higher efficiency
rating) [7].

Speed control. As in most countries of the world, many motors used in China operate under varying load
conditions and can potentially benefit from speed control technologies. Speed control technologies
available in China range from eddy-current drives to two- and multi-speed motors to electronic variable
speed drives (VSDs). In general, use of these technologies is limited, with less than 10% of motor
systems in China using any of these measures (studies in China estimate that up to 70% of motor
applications can potentially benefit from speed control technologies). Moreover, flow control measures in
use are mainly of low efficiency such as baffle plates or valves and the use of VSDs is low.
Domestic VSD production totals approximately 15-20 MW annually, whereas, imported products total
approximately 400 MW. Thus, imported VSDs have more than a 90% share of the Chinese market, even
though imported products are subject to an import duty. Chinese made VSDs are not of sufficient quality
to meet market demands and also lack some features desired by purchasers. The high price of imported
VSDs restricts their use. The current market price for small-medium sized VSDs (for motors of 200 kW
or less) is approximately RMB 800-1200/kW ($95-145/kW) while the price for larger capacity VSDs is
RMB 1800-2500/kW ($215-305/kW).
Based on surveys in the metallurgical, chemical and building material sectors, energy saving potential
through motor speed control can be as high as 40 billion kWh/year in China. Energy savings in good VSD
applications typically ranges from 20 to 40% and the investment in these good applications can be
recovered in 1-3 years (CECIDC 2000).

                         Table 5: Comparative Efficiency of Chinese Motor Series.
                   Motor Size                                Efficiency
               kW             hp         JO               Y             Y2              Y2e
               0.75            1         76.5           74.5           73.0             75.5
               3.75            5         85.0           84.5           84.0             86.0
                15            20         88.0           88.5           89.0             91.0
                45            60         91.0           92.3           93.0             94.2
                90           125         92.0           93.5           94.2             95.0


System design. Motor systems in China are traditionally designed by Design Institutes which function
somewhat like architectural and engineering firms in Western countries. In China, each industrial sector
(e.g. steel and petroleum) has its own design institute or institutes. These design institutes are in many
cases very conservative and often overly emphasize system safety in motor system design. They often
rely on past experiences and even copy existing designs in some cases. These practices often lead to
motor oversizing resulting in low system efficiency. In addition, the design engineers are often
                                                                                                          22
specialized on certain specific subjects and are often not familiar with energy conservation issues. They
tend to use existing or old products and equipment and are not aware of the latest energy efficient
products.




Possibilities for Reducing Motor System Energy Use in China
There are large opportunities to improve the efficiency of motor systems. Electric motors in China are
approximately 2-4% less efficient on average than motors in the US and Canada. Fans and pumps in
China are also commonly 3-5% less efficient than in developed countries. Even more importantly,
motors, fans, pumps, air compressors and other motor-driven equipment are frequently applied with little
attention to system efficiency. More optimized design, including appropriate sizing and use of speed
control strategies, can reduce energy use by 20% or more in many applications. Thus, motor system
optimization is probably the single biggest source of motor system energy savings. Unfortunately, few
Chinese enterprises use or even know about these energy-saving practices. Studies in the US indicate that
by using all of these techniques in cost-effective applications, motor energy use can be reduced by about
28-42%. Opportunities in China are probably even greater due to the lower average current efficiency of
Chinese motor systems [7].




            Fig. 5. Comparison of EPAct and European Efficiency Standards to Chinese Y and Y2 Motor
                                              Efficiencies.

Minimum efficiency standards for motors. Although motor efficiency is a part of product
specifications for Y and Y2 series motors, there is not a requirement that each manufacturer has to test
and report the efficiency of their products. Due to price pressure in the market, experts estimate that to
reduce material costs, manufacturers representing more than 20% of motors in the market do not reach the
published efficiencies in the Y and Y2 specifications. To address this situation, the China State Bureau of
Technical Quality Supervision (with assistance from IIEC/ICA) is currently developing a minimum
                                                                                                        23
efficiency standard for motors. The standard is currently in draft form and calls for motors to meet the
“Efficiency 2” level developed CEMEP (a European association of individual-country motor
manufacturer associations) (Exico 2001). This efficiency level is illustrated in Figure 5 which also
includes information on Chinese Y and Y2 motors as well as the US Energy Policy Act (EPAct)
minimum efficiency standard.
In addition to developing new motor standards, the program will also investigate appropriate mechanisms
for implementing these standards. Past Chinese government efforts to ban particularly inefficient products
have met with mixed success and thus there is a need to develop improved legal, regulatory and voluntary
implementation frameworks.

Energy, Demand, and Dollar Savings Analysis

Calculating Annual Energy and Demand Savings
To determine the annual dollar savings from the purchase of an energy efficient motor, you first need to
estimate the annual energy savings [8]. Energy efficient motors require fewer input kilowatts to provide
the same output as a standard-efficiency motor. The difference in efficiency between the energy-efficient
motor and a comparable standard motor determines the demand or kilowatt savings. For two similar
motors operating at the same load, but having different efficiencies, Equation 6-1 is used to calculate the
kW reduction. The kW savings are the demand reduction. The annual energy savings are then calculated
as shown in Equation 6-2.
Equations 6-1 through 6-3 apply to motors operating at a specified constant load. For varying loads, you
can apply the energy savings equation to each portion of the cycle where the load is relatively constant for
an appreciable period of time. The total energy savings is then the sum of the savings for each load
period. The equations are not applicable to motors operating with pulsating or random loads or for loads
that cycle at rapidly repeating intervals.

Equation 6-1




                                                                                                         24
Equation 6-2




You can now use the demand savings and annual energy savings along with utility rate schedule
information to estimate your annual reduction in operating costs. This calculation of total annual cost
savings is shown in Equation 6-3. Be sure to apply any seasonal and declining block energy charges.
Equation 6-3




Assessing Economic Feasibility
Because of better design and higher quality materials, premium efficiency motors typically cost 15 to 30
percent more than their energy efficient counterparts. In many situations (new motor purchase, repair, or
motor replacement) you quickly recover this price premium through energy cost savings. To determine
the economic feasibility of installing premium efficiency motors, examine the total annual energy savings
in relation to the price premium. A Motor Energy Savings Calculation Form is attached in [8]. Most
industrial plant managers require that, based on a SPP analysis, investments be recovered through energy
savings within one to three years. The simple payback is defined as the period of time required for the
savings from an investment to equal the initial or incremental cost of the investment. For initial motor
purchases or replacement of burned-out and rewindable motors, the simple payback period for the extra
investment in an premium efficiency motor is the ratio of the price premium (less any available utility
rebate) to the total annual electrical dollar savings. This calculation is shown in Equation 6-4.




                                                                                                      25
Equation 6-4




For replacements of operational motors, the simple payback is the ratio of the full cost of purchasing and
installing a new premium or energy efficient motor relative to the total annual electrical savings. This
calculation is shown in Equation 6-5.

Equation 6-5




Example:
The following ana lysis for replacing a 100 hp TEFC motor operating at 75 percent of full rated load
illustrates how to use Equations 6-1 through 6-4 [8]. The analysis determines the cost-effectiveness of
purchasing a replacement premium efficiency motor having a 3/4-load efficiency of 95.7% instead of an
energy efficient motor.
Kilowatts saved:
From Equation 6-1



This is the amount of power conserved by the energy efficient motor during each hour of use. Multiply
this by the number of operating hours at the indicated load to obtain annual energy savings.
Energy saved:

                                                                                                       26
From Equation 6-2


Assuming utility energy and demand charges of $0.04/kWh and $5.00 per kW per month:
From Equation 6-3



In this example, installing a premium efficiency motor reduces the utility billing by $576 per year. The
simple payback for the incremental cost associated with a premium efficiency motor purchase is the ratio
of the price premium or incremental cost to the total annual cost savings.
Assuming a price premium of $900, the simple payback on investment is:
From Equation 6-4




The additional investment required to buy an energy efficient motor is recovered within 1.6 years.
Premium efficient motors can often rapidly pay for themselves through reduced energy consumption.
After this initial payback period, the annual savings will continue to be reflected in lower operating costs
and will add to your firm‟s profits.

CONCLUSIONS
We need to learn how to best utilize energy, both in existing and in new applications.
Reducing power consumption is one of the greatest ways to overcome limited power resources.
Energy efficiency, of course, should be reflected back into the education of young people. It is absolutely
necessary to consider this in universities where engineers are educated.




                                                                                                         27
                                          REFERENCES

1. Opportunities for Energy Savings in the Residential and Commercial Sectors with High-Efficiency
Electric Motors, Final Report, Prepared for U.S. Department of Energy, Contract No. DE-AC01-
90CE23821.
2. Product Testing: Magna Drive, Report No.1, Prepared by Motor Systems Resource Facility, Oregon
State University, Report #00-048.
3. Varriable Speed Pumping, Executive Summary, DOE/GO-102004-1913, May 2004.
4. Improving the Penetration of Energy-Efficient Motors and Drives, Contract Nº.: 4.1031/Z/96-044,
Contractor: ISR – University of Coimbra (Portugal), project sponsored by European Commission,
Directorate-General for Transport and Energy, SAVE II Programme 2000.
5. www.epn-online.com
6. www.bodospower.com
7. (Nadel et al. 2001) The China Motor Systems Energy Conservation Program: A Major National
Initiative to Reduce Motor System Energy Use in China. Proceedings of the 2001 ACEEE Summer Study
on Energy Efficiency in Industry, Tarrytown, NY, July 25-27 2001.
8. Energy Management for Motor Driven Systems, OFFICE OF INDUSTRIAL TECHNOLOGIES,
ENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY.




                                                                                               28
                                                                                           Annex A

                      IEC publications for electrical machines



  IEC, ISO, DIN, EN                                 TITLE

EN 60034-1             Rotating electrical machines - Part 1: Rating and performance
DIN EN 60034-1
IEC 60072-1            Joining dimensions and accordance of output ratings or type IM
DIN 42673              B3
IEC 60072-1            Joining dimensions and accordance of output ratings or type IM
DIN 42677              B5, IM B10, IM B14
EN 60034-5             Rotating electrical machines-Part 5: Degrees of protection
DIN EN 60034-5         provided by the integral design of rotating electrical machines
                       (IP code)
EN 60034-6             Rotating electrical machines-Part 6: Methods of cooling (IC
DIN EN 60034-6         code)

EN 60034-7             Rotating electrical machines - Part 7: Classification of types of
DIN EN 60034-7         construction, mounting arrangements and terminal box position
                       (IM code)
EN 60034-9             Rotating electrical machines - Part 9: Noise limits
DIN EN 60034-9

EN 60034-12            Rotating electrical machines - Part 12: Starting performance of
DIN EN 60034-12        single-speed three-phase cage induction motors for voltages up
                       to and including 690 V, 50 Hz
EN 60034-8             Rotating electrical machines. Terminal marking and direction of
DIN EN 60034-8         rotating

EN 60034-14            Rotating electrical machines. Level of vibrations
DIN EN 60034-14
БДС EN 60034-14
IEC 60072-1            Cylindrical shaft ends of rotating electrical machines
DIN 748 Tell 3
IEC 60038              Standard voltages recommended by IEC
DIN IEC 60038
EN 60252               Capacitors
DIN VDE 560-8
EN 55014               Electromagnetic compatibility
DIN VDE 0875
БДС EN 55014
EN 60034-18-1          Rotating electrical machines – Part 18: Functional evaluation of
БДС EN 60034-18-1      insulation systems




                                                                                               29
Annex B




    30
                                        LIST OF FIGURES
1) Alternative Methods of Fluid Flow Control: a) Throttling; b) Motor Speed Adjustment.
2) Power Factor Comparisons for Control by Throttling and VFD.
3) Typical life cycle cost LCC components for a mediumsized industrial pumping system.
4) Two pumping systems with same output: (a) Conventional system (Total Efficiency = 31%);
(b) Energy-efficient pumping system combining efficient technologies (Total Efficiency = 72%).
5) Comparison of EPAct and European Efficiency Standards to Chinese Y and Y2 Motor Efficiencies.

                                             LIST OF TABLES
1) Estimation of motor electricity consumption by power range, by 2015 based on the average growth
rates, assuming 1.2% and 1% growth rates in the industrial and in the tertiary sectors, respectively.
2) Economics of EEM or standard motor purchase/repair scenarios for a 45 kW, 1500 rpm motor.
3) Potential Electricity savings in the year 2015.
4) Estimated total electricity savings potential in TWh pa, by 2015.
5) Comparative Efficiency of Chinese Motor Series.

                                            ACRONYMS
AC – alternating current
ACI – autonomous current inverter
BJT – bipolar junction transistor
BLDC motor – brushless direct current motor
CNC – computer numerical control
CSE – cost of saved energy
DC – direct current
DSC – digital signal controller
DSP – digital signal processors
EEM – energy efficient motor
EIA – European Information Administration
EMI – electronic magnetic interference
EPAct – US Energy Policy Act
FOC – field-oriented control
HVAC – heating, ventilating, and air conditioning
IEC – International Electrotechnical Commission
IGBT – insulated gate bipolar transistor
IM – induction motor
LCC – lige cycle cost
NEMA – National Electrical Manufacturers Association
OEM – original equipment manufacturer
PFC – power factor correction
PMSM – permanent magnet synchronous motor
RISC – reduced instruction set computer
RMB – The Renminbi (sign: ¥; code: CNY) is the official currency of the People's Republic of China
rpm – revolution per minute
SPP – simple payback period
VFD - variable-frequency drive
VSD - variable-speed drive
ZVEI - German Electrical and Electronic Manufacturers' Association



                                                                                                     31
                    «MOTOR IN VFD»
                  SCHEME OF PROGRAM




                     Converters


   Motors                             Transformers



                    Experiments

   Loading                              Loading
characteristics                       tachograms




Work analysis        Selection          Design




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posted:9/20/2011
language:English
pages:32