Working Principle, Function and Selection of MCCB

When the current exceeds the trip setting, Moulded Case Circuit Breaker (MCCBs) automatically cut off the current. The housing of a device is Plastic housing that uses a plastic insulator to isolate between the grounded metal part and conductors. Thermal magnetic trip units are present in molded case circuit breakers, while solid-state trip sensors are used to equip large molded case circuit breakers. The molded case circuit breaker can hardly be serviced due to the very compact structure.

Molded Case Circuit Breaker Working Principle

The main low voltage circuit breaker contact is operated electrically or manually. The main contact in the closing position is locked by the free release mechanism locks after the main contact is closed. With the main circuit, the thermal element of the thermal release and the coil of the over-current release are in series. With the power supply, the coil of the under-voltage release is in parallel.

To make the free tripping mechanism act, the armature of the over-current release is closed when the circuit is seriously overloaded or short-circuited. The main circuit is disconnected by the main contact.

The thermal element of the thermal release will be heated When the electronic circuit is overloaded, which will push the free release mechanism to act and bend the bimetallic sheet. The main circuit will be disconnected by the main contact.

The armature of the under-voltage release releases when the circuit is under voltage. As a result, the main contact disconnects the main circuit, and the free release mechanism act.

To make the main contact will disconnect the main circuit and free tripping mechanism act, the armature of the shunt release will be closed when the shunt release button is pressed.

Role of the Moulded case circuit breaker from Moulded Case Circuit Breaker Manufacturer:

• To ensure the safe operation of the system, it can cooperate with the automatic device and protection device to cut off the fault current quickly to prevent the accident from expanding in case of system failure.
• Under normal conditions, you must disconnect and connect the load and no-load current in the high-voltage circuit.

Moulded case circuit breaker Selection

The cost-performance ratio is the key factor to choose among many products after the parameters and type of circuit breaker are determined. The circuit breaker should be reliable and safe under the condition of meeting the basic requirements. Having certain extensibility, such as adding module units to realize function expansion, adjusting to adapt to the changes of future load in a certain range, etc. is better.

According to the specific conditions, the category is selected first. According to the requirements for protection and the rated current of the circuit, the specific parameters are determined. The molded case circuit breaker is preferred when the short circuit current is small and the rated current is below 630A.

Frame circuit breaker (ACB) or MCCB Circuit Breaker with good performance can be used instead although the rated current is relatively large. Whether the current limiting capacity of the circuit breaker can meet the requirements for the branch with a large short-circuits current must be paid attention to. The circuit breaker must have this function when leakage protection is required.