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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)

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Precision variable frequency drive may 07 13
Precision Variable Frequency DriveMay 07-13

Client: Jim WalkerAdvisor: Dr. AjjarapuTeam Members:Matt ShriverJason KilzerNick NationDave ReinhardtApril 24, 2007

Presentation outline
Presentation Outline

  • Introductory Materials (Nick)

  • Project Approach & Design (Jason)

  • Testing and Implementation (Matt)

  • Closing Materials (Dave)

List of definitions
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
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
Operating Environment

  • Indoors

  • No extreme conditions

  • Near power outlet

Intended use
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 design.

  • This drive shall not be used to power any control circuits.

Intended users
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 VFD.


  • 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
Expected End Product

  • Precision variable frequency drive

  • Portable strobe system

  • One-page quick users guide

  • Circuit diagrams and parts list

Present accomplishments
Present Accomplishments

  • Research technologies (100%)

  • Simulate entire system (100%)

  • Purchase components (100%)

  • Build components (85%)

  • Test components (70%)

  • Build entire system (70%)

Project definition activities
Project Definition Activities

  • Develop a VFD that will provide a precise frequency that can be changed.

  • A strobe light will also be included to measure the RPM of the electric motor.

Research activities 1 of 2
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
Research Activities (2 of 2)

  • IGBT Bridge

    • Provides power separation between PWM circuits and power supply circuitry

    • Generates pulses

Precision variable frequency drive
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 motor


  • Pulse Width Modulation Circuits

  • IGBT Bridge and Filter Circuits

  • Power Supply Circuits

Power supply components
Power Supply Components

  • Astrodyne Power Supply (PT-45C)

    • Input: 120 VAC

    • Outputs: +/-15V, +5V

  • Filament Transformer

    • Primary Winding: 117V

    • Secondary Winding: 8V

Filter input output waveforms
Filter Input/Output Waveforms

Input and Output Waveforms of the Low Pass Filter

Implementation and testing
Implementation and Testing

  • Function generator chips

  • Amplifiers

  • Comparator and Inverter

  • IGBT’s

  • Filter

  • Strobe light system

Sine triangle generator chips
Sine & Triangle Generator Chips

  • Built and tested on breadboard

Amplifiers comparator and inverter circuits
Amplifiers, Comparator, and Inverter Circuits

  • Built and tested on breadboard

Comparator testing
Comparator Testing

Comparator Chips

  • UA741 Op Amp

  • LM319N High Speed Comparator


  • Lab Function Generators

  • Function Generator Chips

Igbt bridge
IGBT Bridge

  • build and test on breadboard

Igbt bridge testing
IGBT Bridge Testing

  • Design overlooked need for delay circuitry

  • Tried multiple timing circuits

    • NE555 Timer Circuit

    • UA741 Op Amp Circuit

Strobe light system
Strobe Light System

Strobe Light Schematic


Detailed Gantt Chart

Deadline schedule
Deadline Schedule

Deadlines Schedule


  • Not produced for commercialization

  • Precision variable frequency drive could be implemented for much less than current market price (~$250)

Additional work
Additional Work

  • Resolve comparator issues

  • Resolve IGBT issues

  • Combine Precision VFD and strobe light system into one product

  • Include feedback loop for total autonomy

Lessons learned 1 of 2
Lessons Learned (1 of 2)

  • What went well

  • Design/Simulation of project

  • Testing

  • 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, vendor)

Lessons learned 2 of 2
Lessons Learned (2 of 2)

  • Technical

  • Implement and test one component at a time

  • Keep it simple

  • Comparator troubleshooting

  • IGBT implementation

  • Non-technical

  • Should have planned a lot more time for implementation

  • Everyone must be on the same page

  • Have a good plan to start

Closing summary
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.