Precision Variable Frequency DriveMay 07-13

Client: Jim WalkerAdvisor: Dr. Ajjarapu

Team Members:Matt ShriverJason KilzerNick 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: 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 knowledgeFrequency range was too high

Reverse Engineer(VPI’s Synchronous Drive System)

Difficulty getting hands on productMany partsLittle understanding of parts

Pulse Width Modulation

One group member familiarPrior understanding of partsCould 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)

Sine Wave

Triangle Wave

Comparator

IGBT Bridge

Inverter

Overall Block Diagram (2 of 2)

IGBT Bridge

Low Pass Filter

Frequency Counter

OutputTransformer

Pulse Width Modulation Circuits

Sine Waveform (Variable

Frequency)

Comparator

Triangle Waveform

Inverter

IGBT Bridge and Low Pass Filter

IGBT Bridge

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

InvertedGate SignalU2

uA741

3

2

74

6

1

5+

-

V+V-

OUT

OS1

OS2

Comparator

-Vcc

V1

TD = 1p

TF = 249.99999uPW = 1pPER = .5m

V1 = .5

TR = 249.99999u

V2 = -.5

Triangle Wave0

Inverter

+Vcc

V2

FREQ = 60VAMPL = .375VOFF = 0

00

U3

uA741

3

2

74

6

1

5+

-

V+V-

OUT

OS1

OS2

+Vcc

-Vcc

0

V35Vdc

Sine Wave

-Vcc

+Vcc

V4-5Vdc

0

Gate Signal

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

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

Schedule

Detailed Gantt Chart

Deadline Schedule

Deadlines Schedule

Project Evaluation (1 of 2)

MilestoneDegree of

Achievement Comments

1. PVFD Project partially metSome milestones were fully achieved while others were not

A. Produce PVFD partially metSome of the items below were attained with others only partially attained or not at all

1) Develop Design for PVFD fully metThe design met all technical requirements, when simulation test were complete

2) Simulation of PVFD partially metFull simulation was completed. However two programs were needed to complete simulation

3) Implementation of PVFD partially metThe design was completely implemented into a prototype

4) Technical requirements satisfied by prototype

partially met See items below.

a) Provide minimum power output of 75 W fully met  

b) Output continuously selectable between 58 and 62 Hz

exceeded Output is selectable between 57.5 and 62.5 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)

MilestonesRelative

ImportanceEvaluation

ScoreResultant

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

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 Risks Planned 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

E-mails 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

Unanticipated Risks Attempts to Manage Risks

Strobe light difficultyThe 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