E.M.T. Australia Pty Ltd by hjkuiw354


									E.M.T. Australia
    Pty Ltd

 Electric Mo tor Co nd itio n
Mo nitoring And D iag no stics

          EMT Australia Pty Ltd
                     IN TRODUCTION
EMT Australia is a recently formed company that deals specifically in
electrical condition monitoring and specialises in electric motors and
generators. EMT has been operating since early 2000 and has a very
loyal customer base that is expanding rapidly.
EMT employees have in excess of 75 years combined experience in
electric motor repair, refurbishment and condition monitoring. This
experience enables EMT to not only monitor and detect problems in
motors but to advise on modification and repair procedures as well.

The equipment utilised by EMT is a mixture of conventional condition
monitoring equipment and the latest technology currently available.
Attached is a summary of the basic tests offered by EMT and their typical
applications and benefits. Information on types of monitoring technology
is also attached for your information.

EMT is experienced in setting up complete motor management packages
and electric motor condition monitoring programs to suit its customer’s
specific requirements. This is completed in conjunction with the customer
and is focused on obtaining maximum benefit without effecting production
requirements or machine operation.
For any further information or assistance please do not hesitate to contact

                                                     Wayne Cox
                                                     EMT Australia

                            EMT Australia Pty Ltd
                     EMT SERVICES
Utilising the latest technologies and procedures EMT offers the following
services -

• 24 hr / 7 days a week support

• Quality Assurance audits

• Complete motor management

• Failure analysis

• Overhaul and repair audits

• Maintenance trending

                                                    • Shutdown audits

                                                    • Trouble shooting

                                                    • Monitoring critical drives

                                                    • Spare motor audits

                                                    • Hire machinery audits

                                                    • Acceptance testing

                            EMT Australia Pty Ltd
Some of the benefits derived from EMT services are as follows -

• Cost effective maintenance planning by targeting identified problems.

• Complete motor asset control.

• Reduced loss of production due to machinery failures.

• Extended life of drives by identifying and addressing problems at early
  stage of development.

• Energy cost savings by identifying low efficiency machines.

• The overall ability to make informed maintenance decisions.

• Greater reliability through analysis of failure mechanisms and modes.

• Reduced overall maintenance costs.

• Detailed repair history through electronic databases.

                           EMT Australia Pty Ltd
There are 6 basic fault zones in an electric motor circuit that can be
monitored and trended to improve motor availability and life cycle.

Power Quality – The condition of the signal (voltage and current) from
the power source applied to the power circuit.

Power Circuit – Includes all connections from the transformer to the

Insulation – Includes all ground wall insulation on all conductors from the
switchgear through and including the motor.

Stator – Includes turn to turn, coil to coil, and phase to phase windings of
the motor.

Rotor – Includes rotor bars, rotor laminations and end rings

Air Gap – The magnetic coupling developed in the air gap between the
rotor and the stator; a non-uniform air gap is called eccentricity.

                            EMT Australia Pty Ltd
The following is an outline of the dynamic and static tests that can be
performed on the 6 fault zones in an electric motor circuit and the type of
motor that the tests can be carried out on.

 Fault Zone       Description                                  Tests Applicable
                                            Current              Power                       Static
                                            Analysis            Analysis                     Tests
                Condition of incoming                        Voltage THD
Power Quality   power signals                                Current THD
                Entire circuit from         Current          Voltage imbalance        Inductive imbalance
Power Circuit   transformer to motor        imbalance        Current imbalance        Resistive imbalance – A C
                                                                                      Resistive readings - DC
                Ground wall insulation of                    Line neutral voltages    Resistance to ground
Insulation      power circuit, cables and                    Zero sequence currents   Capacitance to ground
                motor winding                                                         Dielectric absorption
                                                                                      Polarisation index
                                                                                      Step voltage testing
                Phase coils within the      High frequency   Current imbalance        Resistance phase / phase
Stator          motor                       analysis;        Impedance imbalance      Resistive imbalance
                                            Current                                   Inductance phase/ phase
                                            imbalance                                 Inductive imbalance
                                                                                      Rotor influence check
                                                                                      Step voltage testing
                Entire rotor including      Pole pass side   Current imbalance        Resistance phase / phase
Rotor           bars, endrings, porosity,   band                                      Resistive imbalance
                laminations                 amplitude;                                Inductance phase/ phase
                                            Current                                   Inductive imbalance
                                            imbalance                                 Rotor influence check
                                                                                      Step voltage testing
                Relationship between        Current          Current imbalance        Inductive imbalance
Air Gap         rotor and stator            imbalance;                                Rotor influence check
                                            High frequency

                                    EMT Australia Pty Ltd
        Test            Induction Synchronous            Wound Rotor                DC
                         Stator   Stator   Field   Stator   Rotor   Resistors   Arm   Field
Resistance to ground       X        X       X        X       X         X        X        X
Capacitance to ground      X        X       X        X       X         X        X        X
Phase Resistance           X        X                X       X         X
Resistive Imbalance        X        X                X       X         X
Phase Inductance           X        X                X       X
Inductive Imbalance        X        X                X       X
Circuit Resistance                          X                                   X        X
Circuit Inductance                          X                                   X        X
Polarisation Index         X        X       X        X       X         X        X        X
Dielectric Absorption      X        X       X        X       X         X        X        X
Step Voltage Testing       X        X       X        X       X         X        X        X
Rotor Influence Check      X        X                X
Synchronous Check                           X
Bar To Bar Test                                                                 X

Resistance To Ground – Temperature corrected RTG tests the ground
wall insulation of the motor and circuit cables, indicating the condition of
the insulation.

Capacitance To Ground – CTG is an additional indicator of the
insulation condition, identifying contamination build-up on the insulation.

                                  EMT Australia Pty Ltd
Phase Resistance – Phase to phase resistance tests the circuit and the
stator coils for resistance, calculates resistance imbalance, and indicates
when these imbalances are unsatisfactory. High resistive imbalances
indicate hot spots, high resistance connections, or coil shorting in the

Phase Inductance – Phase to phase inductance tests the circuit, stator
coil, iron and rotor components for inductive imbalances and indicates
when these imbalances are unsatisfactory. High inductive imbalances
indicate winding faults and rotor defects.

Dielectric Absorption & PI - A one-minute or ten-minute insulation test
can be performed on both AC and DC motors. If time is short, a one-
minute test, called a Dielectric Absorption (DA) test, can be performed. A
DA ratio is calculated and a profile of RTG vs. time is plotted. If time is not
a concern, a ten-minute test, called a Polarisation Index (PI) test, can be
performed. A PI ratio is calculated and a profile of RTG vs. time is plotted.
The profiles developed can be used to determine the condition of the
motors insulation system.

                             EMT Australia Pty Ltd
Rotor Influence Check – The rotor influence check (RIC) is performed to
isolate problems to either the rotor or stator in a motor. As the rotor is
turned by hand, a plot of its influence on the stator coils is developed
using inductance measurements. If the influence on the stator coils is
uniform, the rotor causes the effects. If the influences on the stator coils
are non-uniform, the stator causes the effects.

Bar To Bar Test – Commutator bar to bar testing can be performed on
DC motors. This aids in trouble shooting a faulty commutator or armature
winding on a DC motor.

Step Voltage Tests -
The information on winding condition available from a polarization test
can be considerably enhanced by observing the variation of current (or
insulation resistance) as the test voltage is increased usually to the
specified DC hipot level. If a weakness exists in the insulation, and if the
ambient conditions are right, breakdown is often preceded by a sudden,
non-linear increase of current with a further increase in voltage. This
enables an experienced operator to interrupt the test at the first sign of
such warning, and if the voltage withstand already achieved is considered
sufficient, return the machine to service until repairs may be conveniently
be scheduled. A suspect winding may be identified, but the precise
location of a weakness in the winding must still be found. The record of
voltage versus current taken during the test can be used in future
comparisons on the same winding.

                            EMT Australia Pty Ltd
Current Analysis
Current analysis utilises 3 phase simultaneous current measurements to
perform rotor bar and eccentricity analysis, in-rush / start-up trending and
high frequency spectrum analysis.

Rotor bar defects result in high temperatures and loss of torque in the
motor. By evaluating the amplitude of the pole pass frequency sidebands
(FP) Emax indicates broken rotor bars before damage can occur to the
stator windings.

Static or dynamic eccentricity results in increased vibration and potential
rotor / stator rubbing. Uncorrected, this condition could cause catastrophic
failure of the stator windings and reduce the life of the bearings. By
evaluating the eccentricity frequency and its associated sidebands, Emax
indicates the condition of the air gap.

The most severe electrical and mechanical stresses applied to a motor
occur during start-up. As much as 7 times full load current can be applied
during start-up. By monitoring the in-rush / start-up current signature,
faults that are evident under these stresses but not during normal
operation can be identified. Trending and comparison of the in-rush /
start-up signature to the motors base line test allows for early indication of
rotor or stator degradation and load ort operational changes.

High frequency spectrum analysis is used to confirm stator winding
defects and perform mechanical fault diagnostics.

Current analysis is performed with the circuit energised. 70% of rated
load, or greater is recommended to maximise the analysis capability of

                             EMT Australia Pty Ltd
Power Analysis
Power analysis utilises 3 phase simultaneous voltage and current
measurements to perform power quality analysis.

Power analysis test results may include indications of voltage imbalances,
voltage spikes, excessive harmonic distortion and stator faults.

High resistance connections result in voltage imbalances and excessive
circulating currents. These circulating currents cause increased winding
temperatures, which lead to insulation damage.

Voltage spikes can be caused by a number of different events, including
starting and stopping of plant loads; use of solid state switching
equipment, such as variable frequency drive units; and power distribution
system configuration changes. Significant voltage spikes stress the
motors insulation system, eventually resulting in insulation failure.

Harmonics are primarily caused by the use of solid state switching
equipment, such as variable speed drives and non-linear loads. The
presence of these harmonics results in excessive heating of the insulation
in the motor, the distribution system, and the drive itself.

Stator faults can be caused by a number of things, including
manufacturing defects, insulation breakdown over the life of the motor,
excessive vibration, and rotor / stator contact due to severe eccentricity or
bearing failure. Emax calculates an impedance imbalance, which aids in
isolating problems between the power distribution system and the stator.

                            EMT Australia Pty Ltd
Reporting using a multiple data base module enables instantaneous
access to all test results and associated data. A specific program is
installed onto customers computers which allows for direct downloads of
test parameters and thus giving the customer “ownership” of all gathered
data for future reference.

With the ability to set alarm and warning levels on individual machines, a
trending program can be customised to suit individual requirements and
give detailed reports on problem drives.

The following is only a sample of the many reports and information that
can be generated from the reporting database.

                                                               MCE Typical Test

                            EMT Australia Pty Ltd

                                                             Typical Insulation Test
                                                                   Typical Spectrum
In addition to condition monitoring services EMT offers complete electric
motor management packages and strategies. The management program
can cover from motor selection and procurement all the way through to
life extension programs.

• Motor system management is basically a plan used to maintain electric
  motor systems at optimal performance for maximum time.
• By following a motor systems management program a company
  ensures that its motor systems are kept at peak operating condition.
• Motor systems management keeps motor systems optimised yielding
  many benefits.

                           EMT Australia Pty Ltd
Improved motor systems lead to :
  • Improved reliability and reduced downtime
       - Fewer failures which means less downtime
       - Quicker response time if and when systems fail by having
          contingency plans in place
       - Preventative and predictive maintenance programs
       - Higher quality motors and motor repairs

  • Lower operating costs and / or increased productivity
      - Lower maintenance costs due to improved reliability
      - Efficient use of all available resources
      - Improved product quality due to improved reliability
      - Lower energy consumption as system is optimised

                          EMT Australia Pty Ltd
• Electric motor systems offer greatest opportunity for performance
• Taking a systems approach is the best option, resulting in greater
  savings than an individual component approach.
• Energy savings are only a part (approx 30%) of the overall
  performance improvements.

                           EMT Australia Pty Ltd
              CONT ACT DET AILS
P.O. BOX 585


0249 872848


0249 873675

Wayne Cox

                       EMT Australia Pty Ltd

To top