# Wright Presentation - Personal Web Pages

```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
[email protected]
Department of Electrical Power Engineering
Mandalay Technological university
Mandalay, Myanmar
Phone: 095-02-88712, Fax: 095-02-88702
Presented by Jason Wright
March 20, 2013
1
Agenda
 Motivation
 Induction Machine Operation: Speed Control
 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:
3
•
•
•
•
•
Costly (VFD &gt; 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
6
Functional Block Diagram
Block Diagram for the Speed Control of Single-Phase
Induction Motor Using Inverter
7
Frequency Control
SG3525A PWM Controller
•
•
•
•
Built-in oscillator
potentiometer or other variable
resistance
Has two outputs to drive two
transistors
The two transistors then drive the HBridge Inverter
IRF 840 Power MOSFET:
8
H-Bridge Inverter
There are 4 valid operative
modes:
1.
2.
3.
4.
T1-T4 ON: Applies positive
T2-T3 ON: Applies negative
T1-T3 ON: Applies zero volts
T2-T4 ON: Applies zero volts
9
Timing Diagram
10
Waveform Comparison
Sinusoidal PWM
(SPWM) with
carrier signal:
Six-Step Drive
Waveform:
Trapezoidal
Waveform from
Latt’s Variable
Speed Drive:
11
Performance
Table of Results:
12
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
13
References
Latt, Aung Zaw, and Ni Ni Win, Ph.D. &quot;Variable Speed Drive of Single Phase Induction
Motor Using Frequency Control Method.&quot; IEEE Xplore. N.p., 20 Apr. 2009. Web. 10
Mar. 2013.
http://en.wikipedia.org/wiki/Induction_motor
http://www.digikey.com/
Photos:
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Latt, Aung Zaw, and Ni Ni Win, Ph.D. &quot;Variable Speed Drive of Single Phase Induction Motor
Using Frequency Control Method.&quot; IEEE Xplore. N.p., 20 Apr. 2009. Web. 10 Mar. 2013.
http://www.mindconnection.com/library/electrical/motorslip.htm