Variable Speed Drive of Single Phase Induction
Motor Using Frequency Control Method
Mr. Aung Zaw Latt
Dr. Ni Ni Win
Department of Electrical Power Engineering
Technological University (Myitkyina)
Myitkyina, Myanmar
azlatt@gmail.com
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
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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
2
Motivation: Induction Machine Operation: Speed Control
• By far most popular type of
motor used by industry
• Governed by the following
Equation:
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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
4
Simple Inverter Circuit
Three Phase Voltage Source Inverter (VSI):
5
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:
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Functional Block Diagram
Block Diagram for the Speed Control of Single-Phase
Induction Motor Using Inverter
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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 HBridge Inverter
IRF 840 Power MOSFET:
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H-Bridge Inverter
There are 4 valid operative
modes:
1.
2.
3.
4.
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.
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Timing Diagram
10
Waveform Comparison
Sinusoidal PWM
(SPWM) with
carrier signal:
Six-Step Drive
Waveform:
Trapezoidal
Waveform from
Latt’s Variable
Speed Drive:
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Performance
No load:
Table of Results:
Under Load:
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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 lowpass filtering provided by the motor windings. Using a simple inverter
consisting of only 4 power MOSFETs reduced drive cost:
Part
Quantity
Unit Cost
Total Cost
SG3525A, PWM Chip
1
0.483
0.483
IRF 840, Power MOSFET
4
0.79223
3.16892
GBPC3508-E4/51, 800V rectifier
1
2.84
2.84
PDB12-F4151-104BF, Pot.
1
0.48
0.48
C 124 Transistor
1
0.02124
0.02124
MJE 12002 Transistor
1
0.47
0.47
7812, 12V DC Regulator
1
0.19375
0.19375
OVERALL COST:
$7.66
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References
Latt, Aung Zaw, 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:
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Latt, Aung Zaw, 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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