Working Principle of Circuit Breaker

•The circuit breaker mainly consists of fixed contacts and moving contacts. In normal "on" condition of circuit breaker, these two contacts are physically connected to each other due to applied mechanical pressure on the moving contacts.

•There is an arrangement to store potential energy in the operating mechanism of circuit breaker, which is realized, if switching signal given to the breaker.

•The potential energy can be stored in the circuit breaker by different ways like by deforming metal spring, by compressed air, or by hydraulic pressure.

•But whatever the source of potential energy, it must be released during operation. Release of potential energy makes sliding of the moving contact at extremely fast manner

•All circuit breakers have operating coils (tripping coils and close coil), whenever these coils are energized by switching pulse, the plunger inside them displaced.

This operating coil plunger is typically attached to the operating mechanism of circuit breaker, as a result the mechanically stored potential energy in the breaker mechanism is released in the  form of kinetic energy, which makes the moving contact to move as these moving contacts are mechanically attached through a gear lever arrangement with the operating mechanism of the circuit breaker.

•After a cycle of operation of circuit breaker, the total stored energy is released and hence the potential energy is again stored in the operating mechanism of circuit breaker by means of spring charging motor or air compressor or by any other means

•This is what we call the mechanical working principle of circuit breaker.