Compact automatic switch with the abbreviation MCCB derived from the name Molded Case Circuit Breaker is a type of breaker that can be cut off under load, which are used to protect short circuit and overload in motors and lighting systems, industrial and other consumers. In other words, these switches are used to protect and disconnect the circuit against reverse current or voltage drop exceeding the permissible limit and extra current drawn by the consumer (overload) and circuit short circuit. The initial switches had larger dimensions and size, and due to their compression and shrinking, these breakers are called compact automatic switches.

Because the compact automatic switch can be cut off under load, it can cut off the circuit when the mains power is connected. This property is considered as an advantage in medium and high pressure circuits. Because many switches are isolators and cannot break the circuit under load.

The difference between automatic and non-automatic switches is that in automatic switches there are various electronic relays to detect overload current and short circuit and other parameters, such as air automatic switch, but non-automatic switches are only for disconnecting and connecting the circuit. and has no electronic relay.

In order to protect the switchboard against fire and to increase the security of the equipment inside the switchboard, compact automatic switches are used. Compact automatic switches are made from 16 to 1600 amperes. Automatic switches are produced in single bridge, double bridge, three bridge and four bridge types. Compact automatic keys have a much longer life and higher cutting power than miniature keys and thermal keys. The cutting power of compact automatic switches is from 16 to 150 kiloamperes.

Compact automatic switches, which are called automatic switches, are divided into the following categories with overload protection, short circuit and earth current leakage:

• Non-adjustable compact automatic key (fix or Fix):

Fix automatic switches are not adjustable in terms of protected current range.

• Adjustable compact automatic key:

This type of key is also divided into two categories: thermal-magnetic adjustable compact automatic key and electronically adjustable compact automatic key.In the type of adjustable automatic switches, it is possible to set the current from 0.6 or 0.8 to 1 times the full load current.