In the past, all fuses need to be replaced by small circuit breakers in order to achieve better safety and control. Unlike fuses, miniature circuit breakers operate as automatic switches and turn on the circuit when there is too much current. Once the circuit returns to normal, it can be closed again without any manual replacement. In most circuits, MCBS is mainly used as a substitute for fuse switches. At present, MCBS is widely used in the range of 10kA MCB to 16 kA capacity. It is a reliable means of protection in all fields of domestic, commercial and industrial applications.

What is a miniature circuit breaker (MCB)?

MCB or miniature circuit breaker is an electromagnetic device that embodies a complete case in moulded insulation material. The main function of 10kA MCB is to switch the circuit, that is, when the current through it (MCB) exceeds the set value, automatically open the circuit (which has been connected to it). If necessary, it can be turned on and off manually like a normal switch.

MCB is a delayed tripping device whose overcurrent controls the operation time. This means that as long as the overload is long enough, it will cause danger to the protected circuit. Therefore, 63 amp MCB do not respond to transient loads, such as switching surge and motor starting current. Generally speaking, these designs are designed to work in less than 2.5 milliseconds under short-circuit faults and 2 to 2 minutes under overload (depending on current level).

MCB is manufactured in different pole versions, such as single, double, triple and quadrupole structures, with different fault current levels. In most cases, 10kA MCB is connected to give two or three pole versions, so that a fault in one line will interrupt the entire circuit, thus providing complete circuit isolation. This feature will be helpful to the protection of single-phase three-phase motor.

These rated 220V DC power supply and 240/415 AC power supply (single-phase and three-phase) have different short-circuit current capacities. Usually, single-phase devices have a load current range up to 100A. Some 63 amp MCB have the ability to adjust their trip current capacity, while some devices are fixed to certain load currents and short circuit ratings.

MCB is used to perform many functions, such as local control switches, disconnectors, fault and overload protection devices, for installation or specific equipment or electrical appliances.

The construction of MCB
MCB embodies the complete shell in the moulded insulation material. This provides a mechanically strong and insulated housing. The switching system consists of fixed and mobile contactors, which are connected with the output line. Metal or current-carrying components are made of electrolytic copper or silver alloys, depending on the rated value of the circuit breaker.
When contacts are separated under overload or short circuit conditions, an arc is formed. All modern 63 amp MCB are designed to handle arc interruption processes, and arc energy extraction and cooling are provided by metal arc separator plates. These boards are kept in proper position with insulating materials. In addition, arc runners are provided to force arcing between the main contacts.