TON DUC THANG UNIVERSITY
FACULTY OF ELECTRICAL AND
ELECTRONICS ENGINEERING
403037
POWER ELECTRONICS
CHAPTER 3: AC VOLTAGE CONTROLLERS AC TO AC CONVERTERS
Hau H. Vo, PhD.
CHAPTER 3: AC VOLTAGE
CONTROLLERS - AC TO AC
CONVERTERS

3.1 Single-phase AC voltage controller
 3.1.1 Resistive load
 3.1.2 RL load
 3.1.3 Inductive load
 3.2 Three-phase AC voltage controller
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OBJECTIVES

Analysis operational principle of AC voltage
controllers – AC to AC converters.

Design,
simulate
and
choose
suitable
converters.
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COURSE LEARNING OUTCOMES
[1] Describe operational principle of SCR & Triac,
operational principal of AC to AC converters.
[2] Explain output waveforms of AC to AC
converters.
[3] Compare output performance of AC to AC
converters.
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COURSE LEARNING OUTCOMES
[4]
Clarify
nature
of
important
quantities,
applications of AC to AC converters.
[5] Compute important quantities, basic AC to AC
converters.
[6] Identify suitable AC to AC converters,
SCR/Triac.
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COURSE LEARNING OUTCOMES
[1]
Describe
operation
principles
of
basic
elements in AC to AC converters.
[2] Compare the output performance of AC to AC
converters.
[3] Compute AC to AC converters.
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CHAPTER 3: AC VOLTAGE
CONTROLLERS - AC TO AC
CONVERTERS

Controls voltage, current & average power
delivered to AC load.

Switches connect & disconnect source &
load at regular intervals.

In phase control, switching takes place
during every cycle of source.
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CHAPTER 3: AC VOLTAGE
CONTROLLERS - AC TO AC
CONVERTERS

In integral-cycle control, source is connected
& disconnected for several cycles at a time.

Application of phase-controlled controller:
light-dimmer circuits & speed control of
induction motors.

Classified as AC-AC converter.
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3.1.1 RESISTIVE LOAD
 SCRs not conduct simultaneously.
 SCR on: load voltage  source voltage.
 SCRs off: load voltage = 0.
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3.1.1 RESISTIVE LOAD
 Either SCR on, switch voltage = 0; neither
SCRs on, switch voltage = vS.
 IAVG in each SCR  zero
 If SCRs on for equal time intervals.
 IAVG in source & load = 0
 IRMS_SCR =
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1
2
IRMS_LOAD
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3.1.1 RESISTIVE LOAD
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3.1.1 RESISTIVE LOAD
Vo,rms
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 sin(2 )

1 

2
2
Vm
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3.1.2 RL LOAD
2
2

Z  R  (L) ,

1



tan
(L R)



Vm

sin(t   )  sin(   )e ( t ) /  for   t  
i0 (t )   Z

0
otherwise

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3.1.2 RL LOAD
Use numerical
method to obtain
extinction angle :
sin(   )  sin(   )e(  ) / 
   
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3.1.3 INDUCTIVE LOAD
Vo, rms  Vm
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 sin(2 )
1 

2
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
3-phase controller with Y-connected resistive load
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
3-phase controller with Y-connected resistive load: load voltage
van for  = 30o
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
Load voltages for a three-phase resistive load for  = 30o.
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
Switch currents for a three-phase resistive load for  = 30o.
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
Load voltage van for  = 75o.
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
Load voltage van for  = 120o.
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
Three-phase controller with -connected resistive load
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
Current waveforms for  = 90o.
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3.2 THREE-PHASE AC VOLTAGE
CONTROLLER
Current waveforms for  = 130o
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SUMMARY AND ASSIGNMENTS
 Summary: configurations and operational
principles of AC voltage controllers - AC to
AC converters.
 Assignment: problems 5.1 - 5.14 in [1].
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