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Back-up Power Supply

Back-up Power Supply. Chris Hopfinger Kevin Rogers December 4, 2003. Motivation. Relates to our specific field of study. We wanted to design a cheaper back-up power supply for a motor. Most of the back-up power supply’s are not specifically designed for use with a motor, just general loads.

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Back-up Power Supply

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  1. Back-up Power Supply Chris Hopfinger Kevin Rogers December 4, 2003

  2. Motivation • Relates to our specific field of study. • We wanted to design a cheaper back-up power supply for a motor. • Most of the back-up power supply’s are not specifically designed for use with a motor, just general loads.

  3. Objectives • To use cheap and simple components to create a power supply for a motor. • Keep motor operating smoothly through the transition from power grid to battery back-up.

  4. Design Considerations • Motor needs a consistent input waveform to operate properly. • Run motor with a 12 volt battery • Need a delay before switching back to the ac line to resynchronize the motor and ac line.

  5. Block Diagram

  6. Phase-Lock Loop

  7. Integrator • Basic integrator circuit. • R and C determined by the time constant of VCO • 1/RC=.05 • Choose R=1k and C=50uF

  8. VCO Tests • ICL8038 chip • Test VCO to determine how to make frequency change. • Vary current into pins 4 & 5

  9. Phase Lock Loop Tests • Test the PLL as a whole. • When the two waveforms were compared their periods had very small error, ~ 1 us. • Phase and Frequency locked over the range of 40-65 Hz.

  10. Inverter Design

  11. Inverter Gate Drives • 1. 1k Hz triangle wave produced by VCO • 2. Modulation function, M(t), from Phase-Lock-Loop • LM311N compares waveforms 1 and 2 outputs 4V logic

  12. Inverter Test

  13. Inverter Tests

  14. Switches Power Relays too expensive and Ideal Switches do not exist • Attempted to use MOSFETS • Rectified Line voltage for control of MOSFETs

  15. Accomplishments • VCO locked with reference frequency • Reasonable output from the inverter

  16. Challenges • The phase comparator was impossible to locate, so one had to be built with NAND gates. • MOSFETs couldn’t be used as in line switches. • Inverter current ratings.

  17. Possible Improvements • Add 12V/170VDC boost-converter to eliminate need for transformer at output of inverter • Add SCR Diode bridge for switching between ac line and inverter • Improve oscillator waveform quality • Improve filtering of higher end frequencies

  18. Questions? Any Questions? We would like to thank all those who aided us with our project, especially Mark Weigert and Prof. Krein.

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