Precision Variable Frequency Drive May 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

Acknowledgements  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.

Solution  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 design.  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 VFD.

Assumptions  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.

Limitations  Minimum Power Output: 75 W  Output Frequency Range: Hz  Frequency Precision: 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 (VPI’s Synchronous Drive System)  Difficulty getting hands on product  Many parts  Little understanding of parts Pulse Width Modulation  One group member familiar  Prior understanding of parts  Could handle low frequencies

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)  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 motor

Design  Pulse Width Modulation Circuits  IGBT Bridge and Filter Circuits  Power Supply Circuits

Overall Block Diagram (1 of 2)

Overall Block Diagram (2 of 2)

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

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 Circuits  Built and tested on breadboard

Comparator Testing Comparator Chips  UA741 Op Amp  LM319N High Speed Comparator Sources  Lab Function Generators  Function Generator Chips

IGBT Bridge  build and test on breadboard

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 Schematic

Closing Material

Resources ItemW/O LaborWith Labor Miscellaneous Parts & Materials $20.00 Device Components$66.90 Project/Poster Printing$0.00 Subtotal$86.90 Labor at $15.00 per hour: Reinhardt, Dave, 142 hrs $2, Kilzer, Jason, 166 hrs $2, Nation, Nick, hrs $2, Shriver, Matt, 245 hrs $3, Subtotal $10, Total$86.90$ 10,609.40

Schedule Detailed Gantt Chart

Deadline Schedule Deadlines Schedule

Project Evaluation (1 of 2) Milestone Degree of AchievementComments 1. PVFD Projectpartially met Some milestones were fully achieved while others were not A. Produce PVFDpartially met Some of the items below were attained with others only partially attained or not at all 1) Develop Design for PVFDfully met The design met all technical requirements, when simulation test were complete 2) Simulation of PVFDpartially met Full simulation was completed. However two programs were needed to complete simulation 3) Implementation of PVFDpartially met The design was completely implemented into a prototype 4) Technical requirements satisfied by prototype partially metSee items below. a) Provide minimum power output of 75 Wfully met b) Output continuously selectable between 58 and 62 Hz exceededOutput is selectable between 57.5 and 62.5 Hz. c) Short-term stability less that 0.01%not attemptedClient not concerned d) Frequency display accurate to Hznot metPVFD has a frequency display accurate to 0.01 Hz. B. Portable strobe systempartially met

Project Evaluation (2 of 2) Milestones Relative Importance Evaluation Score Resultant Score Problem Definition15%100%15.0 Research10%90%9.0 Technology Selection5%100%5.0 End Product Design15%70%10.5 Prototype Implementation15%60%9.0 End Product Testing10%50%5.0 End Product Documentation5%70%3.5 Project Reviews5%90%4.5 Project Reporting10%100%10.0 End Product Demonstration10%50%5.0 Total100% 76.5

Commercialization  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 autonomy

Lessons Learned (1 of 2) 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) What went well Design/Simulation of project Testing

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 Potential RisksPlanned Management Cost (Over Budget) The group was given $300 ($150 - senior design; $150 - client). If the cost was less than $75 over budget the group members would chip in some money. Lazy Group Member s would be sent detailing group members responsibility along with due date. Design does not meet Client’s specifications The client would be contacted and the lack of performance would be discussed. Input for client will determine where the project is to go.

Unanticipated Risks Attempts to Manage Risks Strobe light difficulty The group found a simple "Do It Yourself" strobe light design with complete parts list and schematics. Comparator not working The group sought advice from advisor, graduate students, and other faculty. Difficulty of producing output voltage of 120 VAC Planned to use a transformer to step-up the voltage.

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