Overload Relay Working Principle Pdf

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Overload relay working principle pdf. The most widely used overload relay is the thermal overload relay where a bimetallic strip is used to turn off the motor. Let us discuss it in the following sections. Overload relay working principle thermal overload relay thermal overload relay construction working and application. Thermal overload is widely used for.

The working principle of thermal overload relay is quite simple but interesting. Working of bimetallic thermal overload relay. A thermal overload relay works on the heat produced by the excessive overload current the heat produced by the overload current is utilized to trip the motor circuit. Thermal overload is widely used for motor protection.

Current flows through the overload relay while the motor is running. In the direct heating method the full current to the motor. An adjustment dial located on the unit allows the ampere trip setting a manual test button. The basic working principle of thermal relay is that when a bimetallic strip is heated up by a heating coil carrying over current of the system it bends and makes normally open contacts.

The bimetal strips are heated by the motor current causing them to bend and activating the trip mechanism after a certain travel which depends on the current setting of the relay. Basically thermal overload relay is an overcurrent protection of the simplest type. Fundamental relay operating principles and characteristics 17 time delay and its definitions some relays have adjustable time delay and others are instantaneous or high speed the term instantaneous means having no intentional time delay and is applied to relays that operate in a minimum time of approximately 0 1 second. An overload relay switch works in characteristics with current over time and is different from circuit breakers and fuses where a sudden trip is made to turn off the motor.

In an over current relay or o c relay the actuating quantity is only current there is only one current operated element in the relay no voltage coil etc. As explained above a bimetallic thermal relay works on heating property of bimetallic strip. Hi friends in this article i am talking about thermal overload relay working principle and its function in a dol starter. Figure below shows a typical thermal overload relay.

The working principle of the above differs a little from each other. Are required to construct this protective relay. Working principle of over current relay. Working principle of thermal relay a thermal relay works depending upon the above mentioned property of metals.

Thermal motor protection relays contain three bimetal strips together with a trip mechanism in a housing made of insulating material. In an over current relay there would be essentially a current coil when normal current flows through this coil the magnetic effect generated by the.