Moulded Case Circuit Breakers Explained
A moulded case circuit breaker (MCCB) is a type of electrical protection device that is used to protect the electrical circuit from excessive current, which can then lead to overloading or a short circuit. In large-scale PV systems for system isolation and protection purposes these breakers are used instead of miniature circuit breakers (MCBs).
Operation of MCCB
Along with a temperature-sensitive device (the thermal element), the MCCB makes use of a current-sensitive electromagnetic device (the magnetic element) so that for protection and isolation purposes it can provide the trip mechanism. This enables the MCCB to provide:
- Overload Protection
- Electrical Fault Protection against short circuit currents, and
- Electrical Switch for disconnection.
Overload Protection
With the help of a temperature-sensitive component, MCCB provides overload protection. This component is essentially a bimetallic contact: a contact that has two metals that when exposed to high temperatures expand at different rates. The bimetallic contact will allow the electric current to flow through the MCCB during the normal operating conditions. Whenever the current exceeds the trip value, the bimetallic contact gets heated and bends away due to the different thermal rates of heat expansion within the contact.
The thermal protection of the MCCB will typically have a time delay so that it can allow a short duration of over current which is commonly observed in some device operations, such as inrush currents seen when starting motors. In these circumstances this time delay allows the circuit to continue to operate without tripping the MCCB.
Electrical Fault Protection against short circuit currents
Based on the principle of electromagnetism, Moulded Case Circuit Breaker Manufacturer provides an instantaneous response to a short circuit fault. When current passes through the MCCB the solenoid that is present in MCCB generates a small electromagnetic field. During normal operation, the electromagnetic field that is generated by the solenoid coil is negligible. However, a large current begins to flow through the solenoid when a short circuit fault occurs in the circuit and as a result, a strong electromagnetic field is established by which the trip bar gets attracted and then opens the contacts.
Electrical Switch for disconnection
In addition to tripping mechanisms, in case of emergency or maintenance operations, MCCB Circuict Breaker can also be used as a manual disconnection switch. When the contact opens an arc can be created.
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