What is Overload Relay?

Overload relay 

An overload relay is an electric component used to protect a motor or a machine from overload. Which prevents our machine from overloading. The amount of current we want to pass through it is set. Which you can set according to the power rating of your motor. 

For example: 
Suppose you have installed a 10 ampere motor, and put this overload relay with it, whose setting is 12 amps. So if ever this motor will draw more than 12 amps of current, then in that condition the overload relay will turn off the supply. 

internal working of overload relay?

Whenever a motor takes more load than its normal load ie more ampere, in that condition the overload relay senses the overload and further sends tripping command to the circuit breaker. Thermal type overload relay is used in overload relay. It has a bimetallic strip, the overload condition is sensed by this bimetallic strip. 

What type of protection does overload relay provide? 

Overload relay provides us two types of protection. 
1) At the time of overload 
2) At the time of short phase failure 

Overload condition is that condition, when we put more load on the machine than the normal load, then the motor starts consuming more current. This condition is called overload. 

The amount of current is set in the overload relay, as much as the normal current supply has to be given, if the motor starts consuming more current than the normal amount, then this overload relay will command to trip the circuit break through bimetallic strips. 

Use of Overload relay

Overload relay is mostly used to provide protection to the motor, if you have ever seen the panel of any big machinery, then you must have seen overload relay with contactor. In this system the overload relay is placed between the contactor and the motor. 

How overload relay works?

Suppose a motor is connected to a contactor and an overload relay. And that overload relay has a setting of 12 ampere current. That motor takes 10 ampere current on normal load, but suddenly for some reason that motor started taking more load up to 20 ampere, then in this condition the overload relay passes more than 12 ampere by sensing the current and trip by giving command to the contactor. will do it. Because the maximum limit of 12 amps of that overload relay was set, it will consider more amps as overload. 

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