What is thermal and magnetic protection in MCCB?

Thermal and magnetic protection are two types of protective mechanisms used in MCCBs (Molded Case Circuit Breakers) to ensure safe and reliable operation of electrical systems.

Thermal protection is designed to protect against overloading. It uses a bimetallic strip or a thermal element to sense temperature changes in the circuit breaker caused by an overload current. When the temperature exceeds a pre-set level, the thermal protection mechanism trips the circuit breaker to open the electrical circuit and prevent damage to the equipment or electrical system. This mechanism is called thermal protection because it relies on heat to trigger the tripping mechanism.

Magnetic protection, on the other hand, is designed to protect against short-circuits. It uses an electromagnetic coil that generates a magnetic field when a short-circuit current flows through the circuit breaker. The magnetic field pulls on the tripping mechanism, causing the circuit breaker to open quickly and prevent the short-circuit from damaging the electrical system or equipment. This mechanism is called magnetic protection because it relies on the magnetic field to trigger the tripping mechanism.

In most MCCBs, both thermal and magnetic protection mechanisms are used simultaneously to provide comprehensive protection against a wide range of faults, including overload and short-circuits. The combination of thermal and magnetic protection mechanisms in MCCBs ensures reliable performance and protection of the electrical system and equipment.