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
  • Request
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: Why Starting Current of Induction Motor is High
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
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Electrical Machines > Why Starting Current of Induction Motor is High

Why Starting Current of Induction Motor is High

Last updated: April 25, 2016 4:49 pm
Editorial Staff
Electrical Machines
No Comments
Share
4 Min Read
SHARE

Starting Current in Induction Motor:

Starting current of induction motor is as high as 5 to 7 times the normal full load current. Therefore different starting of induction motor, methods such as (star delta starter, auto transformer starter and other starting methods) are employed in order to reduce the high starting currents of induction motor.

Why High Starting Currents:

Induction motor can be compared to an electrical transformer with the secondary short circuited. Primary winding of the transformer can be compared to the stator winding of the induction motor and the rotor winding is considered as the short circuited secondary winding of the transformer.

Starting Current in Induction MotorInduction motor circuit model is shown in the figure. From the model of Induction motor we can observe that induction motor consists of two branch circuits which are in parallel

  • Magnetizing component circuit
  • Resistance and reactance circuit

Magnetizing component of current flowing through induction motor is proportional to the applied voltage and is independent of load on the motor similar to transformer .

Resistance and leakage reactance circuit consist of resistance and leakage reactance of stator and rotor of induction motor connected in series. A load resistance (variable) is connected in series to the fixed rotor and stator impedance. During starting of the motor, slip will be one. Therefore if we calculate the total impedance offered (stator and rotor impedance) to the inrush currents during starting of induction motor which is minimum resulting in high inrush currents during starting of the motor.

When 3 phase voltage applied across the stator winding for starting of induction motor, high inrush currents magnetize the air gap between the stator and rotor. An induces emf is generated in the rotor windings of the induction motor because of the rotating magnetic field. This induced emf produces electrical current in rotor windings. Current generated in the rotor  windings produces a field which in turn produces torque to rotate the motor. Once the rotor starts picking up the speed, current drawn by the machine decreases. The time required for staring of the motor depends on the time required for the acceleration which depends on the nature of the connected load.

Disadvantages of High Starting Currents in Induction Motor:

High inrush currents drawn by induction motor during starting can result in large dip in connected bus voltages. This dip in bus voltages can impact the performance of other motors operating on the bus. Voltage dips during starting of large motors can trip some of the motors operating on the same bus. Care should be taken to limit the inrush currents during starting of the motor by employing proper starting methods

For large motors life of the machine depends on the number of startings. High inrush currents can cause increase in the temperature of the machine, damages the insulation and can reduce the life of the machine

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

100+ Questions and Answers on Motors and Generators
Why Armature is placed on Stator for Synchronous machines
Parallel Operation of Alternators
Difference between Permanent Magnet BLDC and DC Motor
Losses of Transformer
Difference Between Squirrel Cage and Slip Ring Motors
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
Leave a Comment

Leave a Reply Cancel reply

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

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Types of Transformers
AC Motor Braking
Zigzag Transformers Theory
Induction Motors Faults and Protection
What is Auto Reclosing?
Differences Between AC and DC Motors
Synchronous Generator Salient Pole vs Non Salient Pole
Advantages of Hydrogen cooling in Synchronous Generators

Keep Learning

Allen-Bradley VFD

AC Motor Speed Control

What is a transformer tap changer?

Difference between Induction motor and Synchronous motor

Synchronous Motor Working Principle

Electrical Machines Objective Questions

Electrical Machines Objective Questions

What happen When Synchronous Generator loss Excitation

Alarm Trip for 24v DC Loop

Advantages & Disadvantages of Synchronous Motors

Induction Motor Operating Characteristics

Learn More

Open Channel Flow Measurement Animation

Open Channel Flow Measurement Principle

PLC Structured Text Program for Light Sequences via Timers

PLC Structured Text Program for Light Sequences via Timers

Ladder Logic Questions and Answers

Ladder Logic MCQ Questions and Answers

Power Triangle

Power Triangle

Ambient Air Quality Monitoring System Principle

Ambient Air Quality Monitoring System Principle

R R-C Firing Circuits Disadvantages

R R-C Firing Circuits Disadvantages

Garage Door Roller Shutter

Shutter Door Control using Motor and Limit Switches

PLC Program for Car Parking

PLC Program for Entry and Exit Control of Car Parking

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

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?