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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

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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)

The prototype

The Prototype

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

Project approach

Project Approach

Present accomplishments

Present Accomplishments

  • Research technologies (100%)

  • Simulate entire system (100%)

  • Purchase components (100%)

  • Build components (85%)

  • Test components (70%)

  • Build entire system (70%)

Approaches considered

Approaches Considered

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

Overall block diagram 1 of 2

Overall Block Diagram (1 of 2)

Overall block diagram 2 of 2

Overall Block Diagram (2 of 2)

Pulse width modulation circuits

Pulse Width Modulation Circuits

Igbt bridge and low pass filter

IGBT Bridge and Low Pass Filter

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

Testing and implementation

Testing and Implementation

Pwm circuits

PWM Circuits

Comparator input output waveforms

Comparator Input/Output Waveforms

Inverter input output waveforms

Inverter Input/Output Waveforms

Igbt bridge and low pass filter1

IGBT Bridge and Low Pass Filter

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

Closing material

Closing Material





Detailed Gantt Chart

Deadline schedule

Deadline Schedule

Deadlines Schedule

Project evaluation 1 of 2

Project Evaluation (1 of 2)

Project evaluation 2 of 2

Project Evaluation (2 of 2)



  • 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

Risk and risk management

Risk and Risk Management

Unanticipated risks

Unanticipated Risks

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.

Demonstration and questions

Demonstration and Questions

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