Inst ToolsInst ToolsInst Tools
  • Courses
  • Videos
  • Q & A
    • Interview
      • Instrumentation
      • Electronics
      • Electrical
      • Practical Questions
    • MCQ
      • Instrumentation MCQ
      • Electrical MCQ
      • Electronics MCQ
      • Control Systems MCQ
      • Analog Electronics MCQ
      • Digital Electronics MCQ
      • Power Electronics MCQ
      • Microprocessor MCQ
      • Multiple Choice Questions
  • EE
    • Electronics
      • Electronics Q & A
      • Electronic Basics
      • Electronic Devices & Circuits
      • Electronics Animation
      • Digital Electronics
    • Electrical
      • Electrical Basics
      • Electrical Q & A
      • Power Electronics
      • Electrical Machines
      • Electrical Animation
      • Power Systems
      • Switchgear & Protection
      • Transmission & Distribution
  • Measure
    • Control Valves
    • Calibration
    • Temperature
    • Pressure
    • Flow
    • Level
    • Analyzers
    • Switches
    • Vibration
    • Solenoid Valve
  • Control
    • PLC Tutorials
    • Control Systems
    • Safety Instrumented System (SIS)
    • Communication
    • Fire & Gas System
  • More
    • Design
    • Tools
    • Animation
    • Basics
    • Formulas
    • Standards
    • TextBooks
    • Common
    • Software
    • Excel Tools
    • Erection & Commissioning
    • Process Fundamentals
    • Videos
    • Books
Search
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Reading: Turning Off SCR – Commutation
Share
Notification Show More
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • PLC Tutorials
  • Control Systems
Search
  • Courses
  • Videos
  • Q & A
    • Interview
    • MCQ
  • EE
    • Electronics
    • Electrical
  • Measure
    • Control Valves
    • Calibration
    • Temperature
    • Pressure
    • Flow
    • Level
    • Analyzers
    • Switches
    • Vibration
    • Solenoid Valve
  • Control
    • PLC Tutorials
    • Control Systems
    • Safety Instrumented System (SIS)
    • Communication
    • Fire & Gas System
  • More
    • Design
    • Tools
    • Animation
    • Basics
    • Formulas
    • Standards
    • TextBooks
    • Common
    • Software
    • Excel Tools
    • Erection & Commissioning
    • Process Fundamentals
    • Videos
    • Books
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Power Electronics > Turning Off SCR – Commutation

Turning Off SCR – Commutation

Last updated: September 19, 2016 4:44 am
Editorial Staff
Power Electronics
No Comments
Share
2 Min Read
SHARE
  • To tum on a thyristor, a low voltage, short duration pulse is applied to the gate (typically 4V, 100µs).
  • Once the thyristor is turned-on, the gate loses control and the thyristor will only turn off when the load current falls virtually to zero, or the thyristor is reverse biased.
  • The thyristor will turn off naturally with a.c. supplies as the voltage reverses (which is called as Natural Commutation), but no such reversal occurs with d.c. supplies and it is necessary to force a voltage reversal if tum-off is to occur. This process is called Forced Commutation. This post will give you a brief introduction about SCR commutation.

VI characteristics of SCR

Commutation:

The process of turning OFF SCR is defined as “Commutation”.

  • In all commutation techniques, a reverse voltage is applied across the thyristor during the turn OFF process.
  • By turning OFF a thyristor we bring it from forward conducting to the forward blocking mode.
  • The condition to be satisfied in order to turn OFF an SCR are:
    1. IA < IH ( Anode current must be less than holding current)
    2. A reverse voltage is applied to SCR for sufficient time enabling it to recover its blocking state.
  • There are two methods by which a thyristor can be turned OFF.
    1. Natural Commutation
    2. Forced Commutation

Natural Commutation:-

  • In AC circuit, the current always passes through zero for every half cycle.
  • As the current passes through natural zero, a reverse Voltage will simultaneously appear across the device.
  • This will turn OFF the device immediately.
  • This process is called as natural commutation, since no external circuit is required for this purpose.

Forced Commutation:

  • To turn OFF a thyristor, the forward anode current should be brought to zero for sufficient time to allow the removal of charged carriers.
  • In case of DC circuits the forward current should be forced to zero by means of some external circuits.
  • This process is called as forced commutation
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

Introduction to Thyristor – History, Types, Principle, Advantages
Power Electronics Objective Questions
Top 100 Power Electronics Projects for Engineering Students
How to test SCR using Multimeter
Thyristor Protection Circuits (SCR) – Types, Principle, Explanation
What is Power Electronics? Evolution, Block Diagram, Advantages
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
208kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Power Electronics – Phase Controlled Half Wave Rectifier RL Load
Types of IGBT
Thyristors – Switching, Two Transistor Model, Advantage, Applications
Crowbar fault protection circuit
Power Electronic Devices Specification and Classification
IGBT – Symbol, Construction, Working, Characteristics, Advantages
SCR Triggering Methods
SCR Switching Characteristics
Thyristor Commutation Techniques – Types, Working Principles
Thyristor Triggering Circuits – Types, Explanation, Waveforms (SCR)

Keep Learning

Static VI Characteristics of Thyristor

Thyristors – Working, VI Characteristics, Turn ON Methods

Half-controlled Rectifier With R Load

Phase Controlled Rectifier – Half Controlled Rectifier with R Load

Full-Controlled Rectifier Working Principle

Single-Phase Mid-Point Converter – Bridge Rectifier with Center Tap

Basics of Thyristor

Basics of Thyristor

Symbol of Transistor

Power Transistor – Structure, Biasing, Characteristics, Advantages

Single Phase Half-controlled Rectifier RL Load With FD

Phase-Controlled Half-Wave Rectifier With Freewheeling Diode

R R-C Firing Circuits Disadvantages

R R-C Firing Circuits Disadvantages

Power MOSFET Symbols

Power MOSFET – Symbol, Types, Working, Characteristics, Advantages

Discover More

Shorted Parallel Circuit

Parallel Short Circuit Faults

Temperature and Humidity Objective Questions

Temperature and Humidity Objective Questions

Three phase inverter Animation

Three Phase Inverter Animation

main controller fails

How does a Redundant Controller comes in line when the Main Controller fails?

hipps

What is High Integrity Pressure Protection System?

Electrical Machines Questions and Answers

Electrical Machines Losses, Efficiency and Regulation Questions

Total Organic Carbon Analyzer Working Principle

TOC Analyzer Working Principle

FactoryTalk View Studio Site Edition Pop-Up Confirm Action

How to Automatically Close Pop-up in FactoryTalk View Studio?

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?