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Precision Variable Frequency Drive May

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					Precision Variable Frequency Drive
May 07-13

                      Client: Jim Walker
                     Advisor: Dr. Ajjarapu

                           Team Members:
                              Matt Shriver
                              Jason Kilzer
                               Nick Nation
                           Dave Reinhardt

                             April 24, 2007
Presentation Outline

   Introductory Materials (Nick)
   Project Approach & Design (Jason)
   Testing and Implementation (Matt)
   Closing Materials (Dave)
The Prototype
List of Definitions
   VFD: Variable Frequency Drive
   PWM: Pulse Width Modulation
   IGBT: Insulated Gate Bipolar Transistor

   Faculty advisor Dr. Ajjarapu
   Client Jim Walker
   Graduate Students
       Ryan Konopinski
       Sheng Yang
General Problem Statement

   The speed control of an AC
    synchronous motor.
   The synchronous motor and the
    subsequent drive mechanism do not
    always keep the correct speed.
   A method is needed to control the
    frequency that is delivered to the
    synchronous motor.

   A precision variable frequency drive
    will allow the user to manually
    change the operating frequency.
Operating Environment

   Indoors
   No extreme conditions
   Near power outlet
Intended Use

   As a drive for a low power AC
    synchronous electric motor.
   This drive was not considered to be
    used on any other type of electric
    motor except for a synchronous
   This drive shall not be used to
    power any control circuits.
Intended Users

   Anyone who desires precise control
    over a small AC synchronous motor.
   An owner of a turntable who needs
    better control over the speed of
    their turntable.
   No technical knowledge will be
    required to operate the Precision

   Constant linkage –An increase in
    motor speed by a certain factor will
    result in an increase in the speed of
    the turntable by the same factor.
   Plug – the power cord from the
    record player can plug into a
    standard three pronged outlet.

   Minimum Power Output: 75 W
   Output Frequency Range: 58-62 Hz
   Frequency Precision: 0.001 Hz
   Frequency Stability: < ± 0.01 %
   12” by 12” by 6” size limitation
   Cost less than $350
Expected End Product

   Precision variable frequency drive
   Portable strobe system
   One-page quick users guide
   Circuit diagrams and parts list
Project Approach
Present Accomplishments

   Research technologies (100%)
   Simulate entire system (100%)
   Purchase components (100%)
   Build components (85%)
   Test components (70%)
   Build entire system (70%)
   Approaches Considered

Crystal Oscillator     No prior knowledge
                       Frequency range was too high

Reverse Engineer   Difficulty getting hands on
(VPI’s Synchronous Many parts
Drive System)      Little understanding of parts

Pulse Width            One  group member familiar
Modulation             Prior understanding of parts

                       Could handle low frequencies
Project Definition Activities

   Develop a VFD that will provide a
    precise frequency that can be
   A strobe light will also be included
    to measure the RPM of the electric
Research Activities (1 of 2)

   Pulse Width Modulation
       Needs small signal variable frequency
        sine wave
       Need small signal triangle wave
       Comparator produce pulses from
        comparison of sine and triangle wave
       PWM would create the control signals
        for the IGBT bridge
Research Activities (2 of 2)

   IGBT Bridge
       Provides power separation between
        PWM circuits and power supply circuitry
       Generates pulses
Precision Variable Frequency Drive

   Ready to use design
   Delivers precise frequency control for low
    power AC synchronous motors
   Strobe light included to measure RPM of

 Pulse Width Modulation Circuits
 IGBT Bridge and Filter Circuits

 Power Supply Circuits
Overall Block Diagram (1 of 2)

 Sine Wave      Comparator

                             IGBT Bridge

Triangle Wave    Inverter
Overall Block Diagram (2 of 2)

                Low Pass     Frequency
                  Filter      Counter

 IGBT Bridge

               Transformer    Output
Pulse Width Modulation Circuits



IGBT Bridge and Low Pass Filter

Power Supply Components
   Astrodyne Power
    Supply (PT-45C)
       Input: 120 VAC
       Outputs: +/-15V, +5V

   Filament Transformer
       Primary Winding: 117V
       Secondary Winding: 8V
Testing and Implementation
PWM Circuits


                                                    +Vcc                                        U3
                                                                                         3                        5   Inverted


                                              U2                                                +          OS 2
                                          3                       5                                               6
                                                                                                                      Gate Signal

                                              +           OS 2                                           OUT
V 1 = .5            V1                                             Gate Signal
V 2 = -.5                                                         6                      2                        1

T D = 1p                                                OUT                                     -          OS 1
T R = 2 4 9.9 9999u                       2                       1                   u A7 41

T F = 2 4 9.9 9999u                           -           OS 1

PW = 1p                                   u A7 41
P ER = .5m          0                                                                                -Vcc
                                                                      +Vcc            -Vcc
Triangle Wave
                                     V2                                   V3             V4
                    V OFF = 0                                    5 Vd c        -5V d c
                    V AM PL = .375
                    FRE Q = 6 0

                                     0                                    0              0
                    Sine Wave
Comparator Input/Output Waveforms
Inverter Input/Output Waveforms
IGBT Bridge and Low Pass Filter
Filter Input/Output Waveforms

  Input and Output Waveforms of the Low Pass Filter
Implementation and Testing

   Function generator chips
   Amplifiers
   Comparator and Inverter
   IGBT’s
   Filter
   Strobe light system
Sine & Triangle Generator Chips
   Built and tested on breadboard
Amplifiers, Comparator, and Inverter

   Built and tested on breadboard
Comparator Testing

Comparator Chips
 UA741 Op Amp

 LM319N High Speed Comparator

 Lab Function Generators

 Function Generator Chips
IGBT Bridge

   build and test on breadboard
IGBT Bridge Testing

   Design overlooked need for delay
   Tried multiple timing circuits
       NE555 Timer Circuit
       UA741 Op Amp Circuit
Strobe Light System

         Strobe Light Schematic
Closing Material
Item                                      W/O Labor   With Labor
Miscellaneous Parts & Materials              $20.00       $20.00
Device Components                            $66.90       $66.90
Project/Poster Printing                       $0.00        $0.00
                             Subtotal        $86.90       $86.90
Labor at $15.00 per hour:
Reinhardt, Dave, 142 hrs                               $2,130.00
Kilzer, Jason, 166 hrs                                 $2,490.00
Nation, Nick, 148.5 hrs                                $2,227.50
Shriver, Matt, 245 hrs                                 $3,675.00
                             Subtotal                 $10,522.50
                                  Total      $86.90   $ 10,609.40

           Detailed Gantt Chart
Deadline Schedule

          Deadlines Schedule
       Project Evaluation (1 of 2)
                                                Degree of
Milestone                                      Achievement     Comments
                                                               Some milestones were fully achieved while others
1. PVFD Project                                partially met
                                                               were not
                                                               Some of the items below were attained with others
A. Produce PVFD                                partially met
                                                               only partially attained or not at all
                                                               The design met all technical requirements, when
1) Develop Design for PVFD                       fully met
                                                               simulation test were complete
                                                               Full simulation was completed. However two
2) Simulation of PVFD                          partially met
                                                               programs were needed to complete simulation
                                                               The design was completely implemented into a
3) Implementation of PVFD                      partially met
4) Technical requirements satisfied by
                                               partially met   See items below.

a) Provide minimum power output of 75 W          fully met

b) Output continuously selectable between 58
                                                exceeded       Output is selectable between 57.5 and 62.5 Hz.
and 62 Hz

c) Short-term stability less that 0.01%        not attempted   Client not concerned

d) Frequency display accurate to 0.001 Hz        not met       PVFD has a frequency display accurate to 0.01 Hz.

B. Portable strobe system                      partially met
Project Evaluation (2 of 2)
                                     Relative   Evaluation   Resultant
Milestones                         Importance     Score       Score
Problem Definition                    15%         100%         15.0
Research                              10%          90%          9.0
Technology Selection                  5%          100%          5.0
End Product Design                    15%          70%         10.5
Prototype Implementation              15%          60%          9.0
End Product Testing                   10%          50%          5.0
End Product Documentation             5%           70%          3.5
Project Reviews                       5%           90%          4.5
Project Reporting                     10%         100%         10.0
End Product Demonstration             10%          50%          5.0
                           Total     100%                      76.5

   Not produced for commercialization
   Precision variable frequency drive
    could be implemented for much less
    than current market price (~$250)
Additional Work

   Resolve comparator issues
   Resolve IGBT issues
   Combine Precision VFD and strobe
    light system into one product
   Include feedback loop for total
 Lessons Learned (1 of 2)

What went well
•Design/Simulation of project

What did not go well
•Problem definition and planning (needed a new plan when we
started implementing)
•Having everyone on the same page (team members, advisor,
Lessons Learned (2 of 2)
•Implement and test one component at a time
•Keep it simple
•Comparator troubleshooting
•IGBT implementation

•Should have planned a lot more time for implementation
•Everyone must be on the same page
•Have a good plan to start
Risk and Risk Management

Potential Risks   Planned Management
Cost              The group was given $300 ($150 - senior design;
(Over Budget)     $150 - client). If the cost was less than $75 over
                  budget the group members would chip in some
Lazy Group        E-mails would be sent detailing group members
Member            responsibility along with due date.
Design does not   The client would be contacted and the lack of
meet Client’s     performance would be discussed. Input for client
specifications    will determine where the project is to go.
Unanticipated Risks
Unanticipated Risks       Attempts to Manage Risks
                          The group found a simple "Do It Yourself"
Strobe light difficulty   strobe light design with complete parts list and

Comparator not            The group sought advice from advisor,
working                   graduate students, and other faculty.

Difficulty of
                          Planned to use a transformer to step-up the
producing output
voltage of 120 VAC
Closing Summary

   An incomplete prototype was
    produced due to difficulties with the
    comparator and the IGBT bridge.
   Estimated final product could be
    commercialized and sold for $250.
Demonstration and Questions