In this note, we are going to learn About Minimum Oil Circuit Breaker or MOCB, also about its construction, working principle, advantages, and disadvantages. Welcome to Poly Notes Hub, an one stop solution for polytechnic notes for diploma engineering students.
Author Name: Arun Paul.
What is Minimum Oil Circuit Breaker?
A minimum oil circuit breaker (MOCB) is a type of circuit breaker used in electrical power distribution networks. It works by utilizing a small amount of insulating oil for arc extinction. When an electrical fault or overload occurs, resulting in excessive current flow, the MOCB interrupts the circuit to protect the equipment and assure its safety.
The MOCB comprises an insulating oil-filled chamber, contacts, and arc extinguishers. When a fault occurs, the increased current flow creates an arc between the contacts. The insulating oil serves to quench the arc, extinguishing it and breaking the circuit.
Construction of MOCB
Below we discuss the construction of this device –
- Gas Vent: The MOCB has a gas vent for releasing any gasses produced during the arc extinction process. This helps to maintain pressure equilibrium within the breaker, ensuring safe operation.
- Arc extinction device: This is a critical component that extinguishes the arc created between the contacts when a fault occurs. Arc extinction can be accomplished by a variety of means, including the use of arc chutes, magnetic blowout coils, or grids containing arc-extinguishing materials.
- Fixed contact: These are MOCB components that stay stationary throughout operation. They are intended to make electrical contact with the moving contacts when the circuit breaker is closed.
- Moving contact: These moveable contacts are in charge of connecting or disconnecting the electrical circuit. When the circuit breaker is closed, the moving contacts come into contact with the fixed contacts, completing the circuit. When the breaker is opened, the moving contacts separate from the fixed contacts, interrupting the circuit.
- Terminals: The MOCB can be connected to the electrical system using the terminals that are provided. For current to pass through the circuit breaker, cables or conductors that are entering into and going out of the device are attached to these terminals.
- Supporting chamber: The contacts, the arc extinction device, and other internal systems of the MOCB are all structurally supported by this chamber. During operation, it aids in keeping these components stable and aligned.
- Drain valve: To remove or drain the insulating oil used in the circuit breaker, the MOCB could have a drain valve. In the event of oil pollution or for maintenance needs, this can be helpful.
Working Principle of MOCB
The Minimum Oil Circuit Breaker (MOCB) works by allowing electrical current to flow continuously during normal operation. However, when a malfunction develops in the electrical system, such as a short circuit or overload, the MOCB senses it and opens its contacts. Because of the rapid current flow, an arc develops between the contacts.
The MOCB uses a variety of arc extinction technologies to quickly cool and deionize the arc, causing it to extinguish. Once the arc is extinguished, the MOCB guarantees that the contacts are completely separated, essentially breaking the circuit and stopping the flow of electricity. After the fault has been resolved, the MOCB can be reset to the closed position, allowing regular operation to resume. Overall, the MOCB’s operating premise is to identify faults, extinguish sparks, and stop circuits to prevent harm and maintain safety.
Advantages of MOCB
Below we listed some merits of this device –
- Compact in size.
- It can easily handled high fault currents.
- It require less maintenance.
- It is versatile and reliable device.
Disadvantages of MOCB
Below we listed some demerits of this device –
- MOCBs contain insulating oil, which might harm the environment if not handled appropriately.
- Periodic maintenance is necessary for the insulating oil used in MOCBs, including contamination and degradation monitoring.
- MOCBs may initially cost more than certain other kinds of circuit breakers.