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Variable Speed Drive of Single Phase Induction Motor Using Frequency Control Method

Variable Speed Drive of Single Phase Induction Motor Using Frequency Control Method. Mr. Aung Zaw Latt Department of Electrical Power Engineering Technological University ( Myitkyina ) Myitkyina , Myanmar azlatt@gmail.com Dr. Ni Ni Win Department of Electrical Power Engineering

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Variable Speed Drive of Single Phase Induction Motor Using Frequency Control Method

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  1. Variable Speed Drive of Single Phase InductionMotor Using Frequency Control Method • Mr. AungZawLatt • Department of Electrical Power Engineering • Technological University (Myitkyina) • Myitkyina, Myanmar • azlatt@gmail.com • Dr. Ni Ni Win • Department of Electrical Power Engineering • Mandalay Technological university • Mandalay, Myanmar • Phone: 095-02-88712, Fax: 095-02-88702 • Presented by Jason Wright • ECGR 6185, Adv. Embedded Systems • March 20, 2013

  2. Agenda • Motivation • Induction Machine Operation: Speed Control • Traditional Variable Frequency Drives • A Simpler Approach for Single Phase Motors • Functional Block Diagram • Frequency Control • H-Bridge Inverter • Timing • Output Waveforms • Performance • Conclusion • References

  3. Motivation: Induction Machine Operation: Speed Control • By far most popular type of motor used by industry • Governed by the following Equation:

  4. Motivation: Traditional Variable Frequency Drives • Costly (VFD > Motor) • Complex • Can be large • More common for three phase motors • DC inverters require high switching frequencies and more switching elements • Can have smoother output

  5. Simple Inverter Circuit • Three Phase Voltage Source Inverter (VSI):

  6. Motivation: A Simpler Approach for Single Phase Motors • Mr. Latt proposes using an H-bridge and a simple digital (ON or OFF) output signal to simulate AC with a DC source. The output voltage is a modified square wave, but given the motor windings’ inherent low-pass filtering, the current waveform approximates a sinusoid. This approach offers several advantages:

  7. Functional Block Diagram • Block Diagram for the Speed Control of Single-Phase Induction Motor Using Inverter

  8. Frequency Control SG3525A PWM Controller • Built-in oscillator • Adjust PWM frequency with a potentiometer or other variable resistance • Has two outputs to drive two transistors • The two transistors then drive the H-Bridge Inverter IRF 840 Power MOSFET:

  9. H-Bridge Inverter • There are 4 valid operative modes: • T1-T4 ON: Applies positive voltage (Vs) to the load. • T2-T3 ON: Applies negative voltage (-Vs) across the load. • T1-T3 ON: Applies zero volts across the load. • T2-T4 ON: Applies zero volts across the load.

  10. Timing Diagram

  11. Waveform Comparison • Trapezoidal Waveform from Latt’s Variable Speed Drive: • Sinusoidal PWM (SPWM) with carrier signal: • Six-Step Drive Waveform:

  12. Performance • No load: • Table of Results: • Under Load:

  13. Conclusion • AC asynchronous motor speed could be controlled by varying the pulse width frequency with a variable resistor. The crude waveform does a decent job at providing a sinusoidal current with the help of the low-pass filtering provided by the motor windings. Using a simple inverter consisting of only 4 power MOSFETs reduced drive cost:

  14. References • Latt, AungZaw, and Ni Ni Win, Ph.D. "Variable Speed Drive of Single Phase Induction Motor Using Frequency Control Method." IEEE Xplore. N.p., 20 Apr. 2009. Web. 10 Mar. 2013. • http://en.wikipedia.org/wiki/Induction_motor • http://ecee.colorado.edu/copec/book/slides/Ch4slide.pdf http://www.onsemi.com/pub_link/Collateral/SG3525A-D.PDF (datasheet for SG3525A) http://www.digikey.com/ • Photos: • Latt, AungZaw, and Ni Ni Win, Ph.D. "Variable Speed Drive of Single Phase Induction Motor Using Frequency Control Method." IEEE Xplore. N.p., 20 Apr. 2009. Web. 10 Mar. 2013. • http://www.mindconnection.com/library/electrical/motorslip.htm • http://ecee.colorado.edu/copec/book/slides/Ch4slide.pdf • http://www.iccfl.com/product_info.php?products_id=8191 • http://www.onsemi.com/pub_link/Collateral/SG3525A-D.PDF (datasheet for SG3525A) • http://www.iccfl.com/product_info.php?products_id=8191 • http://www.aliexpress.com/compare/compare-irf840-mosfet.html

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