Circuit breakers types are mainly distinguished at the normal current they are supposed to carry and the short circuit breaker types that it can safely interrupt. When a short circuit occurs current more than the normal expected rate flows through the circuit which leads to the formation of the ARC which results in the flow of current despite the separation of contacts. This situation may lead to a a very serious threat to the circuit and the equipment it’s installed in, so the Circuit Breakers are designed with various features to overcome such formation of ARC and extinguish them in a controlled manner, These features and medium to control ARC varies from size and usage accordingly.
· Low Voltage Circuit breakers: these are very common type of circuit breakers, they deal with a low voltage (below 1000V) it comprises of following circuit breakers:
1. MCB (Miniature Circuit Breaker) – expected current rate is advised more than 100 A. functions on a trip mechanism normally, thermal and thermal magnetic breakers fall under this category. These MCB’s are categorized in type B, type C, Type D according to the amount full load of current.
2. MCCB (Molded Case Circuit Breaker) –expected current up to 2500 A.
Trip function can be adjustable. Large units can be designed to access remotely.
· Magnetic circuit breakers: they use a Solenoid (electromagnet),which pulls the contacts increasingly by the increasing rate of current. As the current in the circuit increases beyond the expected rate the electromagnet helps drop a latch, which leads to a spring action to open the contacts. Temperature does delay the time but not the current rating.
· Thermal Magnetic Circuit breakers: this Circuit breakers is mainly found on distribution boards, it’s functioning is described by its name as it uses both thermal for long term over current and magnetic for short circuits. The thermal portion helps in opening contacts more promptly .
· Common Trip breakers: this Circuit breakers type applies when more than one conductor occurs. To ensure a common trip for all the working conductors, when any one of them trips. They can comprise of many different trip mechanism or use for small breakers can be tied externally with the poles together. Two-four breakers are used when disconnecting multiple phase or to make sure no current flows through the same network.
· Medium Voltage Circuit breakers: its expected voltage rate varies from 1 – 72 kV, according to usage could be used in indoor as switch gear & outdoors as a Component in a substation. They are classified by the medium used to extinguish the ARC.
1. Vaccum Circuit breakers
2. Air Circuit Breakers
3. SF6 (Sulphur hexafluoride) OR Gas Circuit Breakers
· High Voltage Circuit Breakers: These are mainly used in power transmission networks.