A relay is a device used for switching and is used in many electrical as well as electronic circuits. It acts as shield guard against extra voltage, current or even heat and protects the gadget as well enable the gadget to perform with great efficiency. As per the expert’s relays are types of switch controlled by an electric current. Basically, relays can be utilized safely switch from low to high voltages and currents. Though there are many types of relays used in the various application, this short article is primarily written to educate the readers and other enthusiasts about the Thermal Relay which is widely used in the areas such as motor control, temperature control devices both in homes as well as in large factories.

Working Principle of Thermal Relays and its Construction

In general, a thermal relay also known as Thermal Overload Protection Relay (TOPR) is a simple device which offers over current protection for all motors used in various applications in homes or in the industries. Basically, this TOPR prevents the motor when it gets overloaded and produces heat as a result. Such events occur when there is an excess current drawn by the motor, and if continued for long, it can ruin the motor itself. In this context, a TOPR is installed which can sense the excess heat and switch off the motor circuit and thereby prevents serious damages.

Let us know what a thermal overload relay is all about. As the general law in physical science, various metals have a different coefficient of thermal expansion. When two different metals which are joined together are heated the metal which has a higher value of the coefficient of thermal expansion will expand more than the other one, and it causes a bend in this bimetallic strip. All the TOPR works in this principle and the switches used in these relays are fitted with the bimetallic strips so that it can trip off when the temperature goes high in the applied motor.

Let us know what a thermal overload relay is all about. As the general law in physical science, various metals have a different coefficient of thermal expansion. When two different metals which are joined together are heated the metal which has a higher value of the coefficient of thermal expansion will expand more than the other one, and it causes a bend in this bimetallic strip. All the TOPR works in this principle and the switches used in these relays are fitted with the bimetallic strips,o that it can trip off when the temperature goes high in the applied motor.

The design of the TOPR is known to be critical, and the relays are made for various specifications and hence used in different applications. Here one should remember the fact that a motor during its general operation produces a certain amount of heat due to self-induction. Hence while designing these thermal sensitive relays, a designer has to consider the optimum temperature generated by the motors and accordingly the suitable relays are to be added to the circuit. This factor is considered to be critical, and hence the buyers need to use the correctly rated relays that can produce the expected results by switching off the motor when there is an excess heat than the desirable thermal level.

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