Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: Synchronous Motor Starting Methods
Share
Notification Show More
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Electrical Machines > Synchronous Motor Starting Methods

Synchronous Motor Starting Methods

Last updated: December 22, 2018 1:25 am
Editorial Staff
Electrical Machines
3 Comments
Share
4 Min Read
SHARE

In the previous article we came to know that synchronous motors are not self starting so to make them start automatically we should add some tweaks.We should rotate rotor near to the speed of synchronous speed,so it attains synchronous speed.We have some fine methods to start the synchronous motor.

They are,

1. Using pony motors.
2. Using small d.c. motor.
3. As a slip ring induction motor.
4. Using damper winding.

1. Pony Motor Method / Induction Motor

Pony motors are small motors mostly induction motors,which are used to run the rotor near to the synchronous speed. Once the rotor attains the synchronous speed, the d.c. excitation to the rotor is switched on.Pony motors are connected to the shaft of synchronous motor only up to it attains synchronous speed.Once the synchronism is established pony motor is decoupled. The motor then continues to rotate as synchronous motor.

In the below figure we tried to show you pony motor connection to synchronous motor.This is not exact arrangement what we use in industries.

Pony Motor Method or Induction Motor

2. Using Small D.C. Machine

This is also similar to pony motor method with some advantages.Mostly this method employed for large synchronous motors.For synchronous motor a dc machine will be connected.This dc machine is used as a d.c. motor to rotate the synchronous motor at a synchronous speed.. Once motor starts running as a synchronous motor, the same d.c. machine acts as a d.c. generator to supply dc to the rotor of syn. motor.This have some advantages like low power usage and easy starting.

3.Using Damper Winding

This is the most used method of starting synchronous motor.In addition to the normal field winding an additional winding consisting of copper bars placed in the slots in the pole faces.Ends of the copper bars are short circuited with the help of end rings.This winding is called damper winding.This damper winding acts as a squirrel cage rotor of an induction motor.

damper-winding-in-salient-pole-rotor

First synchronous motor runs as induction motor due to the damper winding at sub synchronous speed.Then d.c. supply is given to the field winding. At some instant motor gets pulled into synchronism and starts rotating at a synchronous speed.As rotor rotates at synchronous speed, the relative motion between damper winding and the rotating magnetic field is zero. Hence when motor is running as synchronous motor, there can not be any induced e.m.f. in the damper winding. So damper winding is active only at start, to run the motor as an induction motor at start.

4. Slip Ring Induction Motor

In this method an external rheostat then can be introduced in series with the rotor circuit. So when stator is excited, the motor starts as a slip ring induction motor and due to resistance added in the rotor provides high starting torque.

Slip Ring Starting Method

The resistance is then gradually cut off, as motor gathers speed. When motor attains speed near synchronous. d.c. excitation is provided to the rotor, then motors gets pulled into synchronism and starts rotating at synchronous speed. The damper winding is shorted by shorting the slip rings. The initial resistance added in the rotor not only provides high starting torque but also limits high inrush of starting current. Hence it acts as a motor resistance starter.

Also Read: Synchronous Motor Working Principle

Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

Types of Generators
Difference between Induction motor and Synchronous motor
Faults in a Transformer
Types of Transformers
How Motor Star Delta Starter Works ?
Losses in a DC Generator
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
3 Comments
  • hackson kedala says:
    January 17, 2018 at 7:09 am

    it is well explained

    Reply
  • Santosh Kopnar says:
    December 3, 2021 at 9:11 am

    Very Easy To Understand Thanks .

    Reply
  • Marius Dickinson says:
    March 2, 2025 at 2:58 am

    I have a question about the pony motor method starting a synchronous motor

    Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
208kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Transformer Tap Changing Working Principle
Transformer Energy Losses & Efficiency
Advantages & Disadvantages of Variable Speed Drives
Synchronous Motor Is Not Self Starting?
6.6kV HV Induction motor Protection
AC Motor Braking
Squirrel Cage Induction Motor vs Slip Ring Induction Motor
Use of line reactors

Keep Learning

DC Motor Applications in Industries

Transformer Open and Short Circuit Tests

What is a transformer tap changer?

Difference between Permanent Magnet BLDC and DC Motor

Applications of Synchronous Motors

Questions and Answers on Motors and Generators

100+ Questions and Answers on Motors and Generators

Electrical-Switches-Working-Animation

Difference between Star and Delta Connections

Allen-Bradley VFD

AC Motor Speed Control

Learn More

how-to-avoid-bad-grounds

How to Avoid Bad Grounds ?

Override Control Functions

Override Control Functions

SFC Language in PLC Programming

SFC Language in PLC Programming

Ccomparator in PLC Programming

Comparator in PLC Programming

Liquid Level Control using Flow Loop

Liquid Level Control using Flow Loop

Power Electronics Objective Questions

Choppers MCQ

Why does SMPS Need isolation - Switch Mode Power Supply

Why does SMPS Need isolation? – Switch Mode Power Supply

Electric Circuits Objective Questions

Electric Circuits Objective Questions – Set 10

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?