Circuit Breaker Operating Mechanism, Must watch video

Typically, the “closing spring” is mechanically charged by a motor and is held in its compressed position by a closing latch. When a close signal releases this latch, this spring pushes against a mechanical linkage to force the breaker contacts closed and, at once, charges the trip spring.
What is Circuit Breaker?
An electrical circuit breaker is a switching device that can be operated manually and automatically for controlling and protecting an electrical power system. As the modern power system deals with huge currents, special attention should be given during designing of a circuit breaker to ensure it is able to safely interrupt the arc produced during the closing of a circuit breaker. This was the basic definition of circuit breaker.

Introduction to Circuit Breaker
The modern power system deals with huge power network and huge numbers of associated electrical equipment. During a short circuit fault or any other type of electrical fault (such as electric cable faults), a high fault current will flow through this equipment as well as the power network itself. This high current may damage the equipment and networks permanently.

Working Principle of Circuit Breaker
The circuit breaker mainly consists of fixed contacts and moving contacts. In normal “ON” condition of the circuit breaker, these two contacts are physically connected to each other due to applied mechanical pressure on the moving contacts. There is an arrangement stored potential energy in the operating mechanism of circuit breaker which is released if the switching signal is 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. The release of potential energy makes the sliding of the moving contact in a speedy manner.
All circuit breaker have operating coils (tripping coils and close coil), whenever these coils are energized by switching pulse, and 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 forms of kinetic energy, which makes the moving contact to move as these moving contacts mechanically attached through a gear lever arrangement with the operating mechanism.

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

Till now we have discussed mechanical working principle of circuit breaker. But there are electrical characteristics of a circuit breaker which also should be considered in this discussion of the operation of the circuit breaker. Let’s have a discussion on electrical principle of circuit breaker.

The circuit breaker has to carry large rated or fault power. Due to this large power, there is always dangerously high arcing between moving contacts and fixed contact during operation of the circuit breaker. Again as we discussed earlier the arc in circuit breaker can be quenching safely if the dielectric strength between the current carrying contacts of circuit breaker increases rapidly during every current zero crossing of the alternating current.

The dielectric strength of the media in between contacts can be increased in numbers of ways, like by compressing the ionized arcing media since compressing accelerates the deionization process of the media, by cooling the arcing media since cooling increase the resistance of arcing path or by replacing the ionized arcing media with fresh gasses. Hence some arc quenching processes should be involved in the operation of the circuit breaker.


Types of Circuit Breaker
According different criteria there are different types of circuit breaker. According to their arc quenching media the circuit breaker can be categorized as:

Oil circuit breaker.
Air circuit breaker.
SF6 circuit breaker.
Vacuum circuit breaker.
According to their services the circuit breaker can be categorized as:
Animation Video Explain the Circuit Breaker Operating Mechanism ( Circuit Breaker Close Coil , Circuit Breaker Trip Coil and Circuit Breaker Charging Spring).

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Circuit breakers allow the flow of energy to be controlled by safely switching currents on and off at all voltage levels of the energy grid. The interrupter and the mechanical drive are the main components that are subject to wear and aging.
In order to ensure the proper operation of a circuit breaker throughout its lifetime, diagnostic tests are performed, such as resistance, timing, minimum pick-up, travel, and power factor.