Electromagnetic attraction type relay - Construction, working and types

Hello guys welcome to my blog. Hope you are all good and well. 

Today we will discuss about, 

  • What is an electromagnetic attraction relay?
  • Construction of an electromagnetic attraction relay
  • Working of electromagnetic attraction relay
  • Types of electromagnetic attraction relay
  • Advantages and disadvantages of attraction relay
  • Applications of electromagnetic attraction relay

Now lets go to discuss about, 

Electromagnetic attraction relay: -

  • An electromagnetic attraction relay is a type of relay which works on the principle of electromagnetic attraction.
  • Electromagnetic attraction means when the coil is energized it produces the magnetic field around it which will attract the moving contacts. 
  • It consists a coil, carrying a current in large amount when fault occurs, produces a high magnetic field around it and attracts the armature or plunger towards it which trips the circuit breaker. 


Construction of electromagnetic attraction relay: -

  • It is cheap and simple in construction. There are mainly two parts in an electromagnetic attraction relay first is relay coil and another is armature or plunger.
  • The coil is placed on the core with various tapping and connect to the supply. The tapping is done to vary the tripping current value according to the demand. 
  • The armature or plunger is connected to a spring which kept the trip or moving contact in open condition.  
  • When a current more than the rating of the relay flow through the coil it gets energized and attracts the armature or plunger toward it. 
Electromagnetic attraction type relay, construction, working
Electromagnetic attraction type relay




Working of electromagnetic attraction relay: -

In normal condition: -

When there is no fault, i.e. over current or over voltage then, the spring force (spring carrying the armature) is more than the electromagnetic attraction force and the armature is in an open condition. In this condition the moving contacts are open.  

Fs > Fe

When a fault occurs: -

The coil is placed on the core with a number of the tappings and connect with the circuit. 
Whenever the current, more than the set value, flow through the coil produces an attractive force which is more than the spring force. And attracts the armature towards it. 
As moving contacts are connected with the armature so they also move towards the electromagnet and close the contacts of the circuit breaker and trip the supply. 

Fe > Fs

Types of electromagnetic attraction relay: -

There are mainly two types of electromagnetic attraction relay as given below: -
  1. Attracted armature type
  2. Solenoid and plunger type

  • Attracted armature type electromagnetic attraction relay: -

  1. The given fig. Shows this type of relay. It mainly consists two parts an armature and a coil.
  2. The coil is placed on the core and act as the electromagnet when current flow through it. 
  3. The armature consist the moving contact and attached to a spring. 
  4. The armature is attracted by the coil whenever a fault occurs in the circuit. 
Electromagnetic attraction type relay, construction, working
Attracted armature type electromagnetic relay


  • Solenoid and plunger type electromagnetic attraction relay: -

  1. The fig. given below shows the solenoid and plunger type relay. 
  2. There is a solenoid in which a moving plunger is placed and a moving contact is also attached to this plunger. 
  3. In normal condition moving contacts are in an open condition as plunger in not attracted by coil and in open condition due to the spring force or due to gravity.  
  4. But whenever a fault occurs then the plunger gets attracted by the solenoid and close the trip contacts of the circuit breaker. 
Electromagnetic attraction type relay, construction, working
Solenoid and plunger type relay




Advantages of electromagnetic attraction type relay: -

  • These types of relay can be operated on AC supply as well as DC supply. 
  • These types of relay are cheap and simple in construction.
  • These are more reliable. 
  • They are fast in operation. 

Disadvantage of electromagnetic attraction relay: -

  • To operate these types of relays we require CT and PT of high burden . 
  • The operation of these types of relay can affect from the pollution, dust, etc. 
  • These types of relay require regular maintenance.  

Applications of electromagnetic attraction relay: -

  • These relays are used to protect the equipment from over voltage and under voltage.  
  • The electromagnetic attraction relay is used to protect the AC as well as DC equipment.  
  • It provides differential protection. 
  • It provided protection of equipment against over current and under current. 


Conclusion: -

  1. The electromagnetic attraction relay is a type of relay which can be used for AC as well as DC supply. 
  2. It protects the equipment from the over voltage as well as over current. 
  3. The electromagnetic attraction relay is simple in construction and fast in operation. 
  4. It may be of armature type or solenoid and plunger type. 

If you have any doubt then tell me in a comment. 

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Thank you. 

Hope article helps you.


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