This document discusses synchronous motor drives and variable frequency control methods. Synchronous motors have higher efficiency than induction motors but are generally more expensive. Variable frequency control can be done through true synchronous mode using an open-loop system or self-controlled mode using a closed-loop system. Methods like V/F control, margin angle control, and power factor control are explored. Voltage source inverters and current source inverters are also discussed for feeding synchronous motors.

1. SOLID STATE DRIVES
UNIT -IV
SYNCHRONOUS MOTOR DRIVES
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Dr.A.Ravi,
Professor,
Electrical and Electronics Engineering
Francis Xavier Engineering
College,Tirunelveli

2. Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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 Torque angle δ is the angle between Rotor
flux and Stator fluxes, both are rotating at
synchronous speed. It is noted that for
synchronous motors the rotor flux axis
lags the stator flux axis by the angle δ
INTRODUCTION

3. INTRODUCTION
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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• Synchronous motor drives are close competitors to
induction motor drives in many industrial
applications.
• They are generally more expensive than induction
motor drives, but the advantages is that the efficiency
is higher

4. VARIABLE FREQUENCY CONTROL
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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The synchronous motor either run at synchronous speed
(or) it will not run at all.
variable frequency control may employ any of the following two modes
1.True synchronous mode (or) Separate controlled mode
2. Self controlled mode

5. Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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 V/f control of synchronous motor
 self-control of synchronous motor:
 Margin angle control
 power factor control-
 Three phase voltage fed synchronous motor
 current source fed synchronous motor
 Applications
CONTENT

6. VARIABLE FREQUENCY CONTROL
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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True synchronous mode (or) Separate controlled mode
Open
loop

7. VARIABLE FREQUENCY CONTROL
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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Self controlled mode
Closed
loop

8. MARGIN ANGLE CONTROL
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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9. POWER FACTOR CONTROL
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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The main aim of
adjustment of power
factor is the variation
of the field current

10. VOLTAGE SOURCE INVERTER (VSI) FED SYNCHRONOUS MOTOR
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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SELF
CONTROL
SEPEARATE
CONTROL
 Square wave Inverters
 PWM Inverter
 Chopper with square wave Inverter

11. VOLTAGE SOURCE INVERTER (VSI) FED SYNCHRONOUS MOTOR
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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Separate control of SM fed square wave inverter

12. VOLTAGE SOURCE INVERTER (VSI) FED SYNCHRONOUS MOTOR
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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Separate control of SM fed PWM inverter

13. VOLTAGE SOURCE INVERTER (VSI) FED SYNCHRONOUS MOTOR
Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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Self control of SM fed square wave inverter

14. Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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Self control of SM fed PWM inverter
VOLTAGE SOURCE INVERTER (VSI) FED SYNCHRONOUS MOTOR

15. Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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Chopper with square wave Inverter
VOLTAGE SOURCE INVERTER (VSI) FED SYNCHRONOUS MOTOR

16. Dr.A.Ravi, Francis Xavier Engineering College,Tirunelveli
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CSI with Individual Commutation
CURRENT SOURCE INVERTER (VSI) FED SYNCHRONOUS MOTOR
Auxiliary thyristors used for
commutation purpose