You may already see or heard most two common names during your work and that is MCCM and ACB. This two switching device is used to control power in load incoming or outgoing side. But it always depends on the designer which type of switching device is appropriate to control a specific amount of load. These two devices have some basic feature and in this post, we will learn “Features of Moulded Case Circuit Breaker (MCCB) and Air Circuit Breaker (ACB) with Advantage.”
A Moulded Case Circuit Breaker or MCCB and Air Circuit Breaker or ACB usually comprise with the following features,
A contact system with arc-quenching and current-limiting means a mechanism to open and close the contacts auxiliaries which provide additional means of protection and indication of the switch positions.
Related: Introduction of Switchgear
Features of Air Circuit Breaker (ACB):
Now a day, a modern air circuit breaker (ACB) is used as an incoming device on the supply side of a low voltage switchboard. It represents the first line of protection on the load side for a power transformer in an electrical substation. It also includes some additional features,
There are a tripping and protection system and it is responsible to open the circuit breaker under fault conditions. It will isolate the device from the bus bar. It is an open construction or the contact system housed in a plastic molding and current ratings from 400 amperes to 6300 amperes.
The advantage of Air Circuit Breaker (ACB):
- ACB doesn’t have any oil inside for any operation. For this reason, there is no chance of a fire hazard caused by oil.
- The duration of the arc is the same for all values of small and high currents interruptions.
- Due to the duration of the arc is smaller that’s means less amount of heat realized from arc to current carrying contacts and for this reason, the service life of the contacts becomes longer.
- The stability of the system can be well maintained by using ACB.
- It requires less maintenance compared to any oil circuit breaker (OCB).
Related: Circuit Breaker Operation Principle
Features of Moulded Case Circuit Breaker (MCCB):
Now the MCCB may be used as an incoming device as we have in our DB board in the factory. But MCCB is more generally used as an outgoing device on the load side (like machine or motor) of a switchboard. There are three features and it includes,
At first, an electronic or thermal/electromagnetic trip sensing system is operated through the tripping mechanism and open the circuit breaker under overload or fault conditions during operation. Second, all parts housed within a plastic molded housing made in two halves. This is the general outlook of an MCCB that we see from outside. Third, the current rating in general from 10 amperes to 2500 ampere.
The fixed contacts are generally mounted on a back panel or within a plastic molding. Moving contacts are usually supported on an insulated bar or within an insulated carriage.
The advantage of Moulded Case Circuit Breaker (MCCB):
- MCCBs are Compact in size. For this reason, it saves considerable space in panel design.
- MCCBs have minimized downtime. Unlike in a fuse-based system, there’s no searching for a replacement fuse. It can be Reset & Switched On again immediately after finding the fault that caused the tripping during operation.
- MCCBs can clear several faults before it is due for replacement.
- MCCBs are “Maintenance Free” and its recurring costs are less.
- When MCCBs are used, then there is no possibility of single phasing due to fault in only one phase.
- Some multi-purpose accessories can be fitted with the MCCB.
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