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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 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 knowledge Frequency range was too high Difficulty getting hands on Reverse Engineer product (VPI’s Synchronous Many parts Drive System) 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) Sine Wave Comparator IGBT Bridge Triangle Wave Inverter Overall Block Diagram (2 of 2) Low Pass Filter Frequency Counter Transformer Output IGBT Bridge 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 Inverter + 7 OS2 2 - V- OUT OS1 5 Gate Signal 6 2 1 uA741 - OS1 uA741 4 0 +Vcc Triangle Wave -V cc VOFF = 0 VA MPL = .375 FREQ = 60 5Vdc 0 -V cc V3 V2 Sine Wave OS2 OUT V- V1 + 4 3 V1 = .5 V2 = -.5 TD = 1p TR = 249.99999u TF = 249.99999u PW = 1p PER = .5m 0 V+ U2 U3 3 V+ +Vcc 7 +Vcc Comparator V4 -5Vdc 0 0 -V cc 5 6 1 Inverted 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 $0.00 $0.00 $86.90 $86.90 Project/Poster Printing Subtotal 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 Total $10,522.50 $86.90 $ 10,609.40 Schedule Detailed Gantt Chart Deadline Schedule Deadlines Schedule Project Evaluation (1 of 2) Milestone Degree of Achievement Comments 1. PVFD Project partially met Some milestones were fully achieved while others were not A. Produce PVFD partially met Some of the items below were attained with others only partially attained or not at all 1) Develop Design for PVFD fully met The design met all technical requirements, when simulation test were complete 2) Simulation of PVFD partially met Full simulation was completed. However two programs were needed to complete simulation 3) Implementation of PVFD partially met The 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 b) Output continuously selectable between 58 and 62 Hz c) Short-term stability less that 0.01% d) Frequency display accurate to 0.001 Hz B. Portable strobe system fully met exceeded not attempted not met partially met Output is selectable between 57.5 and 62.5 Hz. Client not concerned PVFD has a frequency display accurate to 0.01 Hz. Project Evaluation (2 of 2) Relative Importance Evaluation Score Resultant 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 Milestones 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 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) 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 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