Circuit Breaker Trip by the following:
- Thermal for overload - This consists of a bi-metal strip which, if heated beyond the normal operating values, becomes deformed, releasing the lock holding the contacts.
- Magnetic for short circuits - This consists of a magnetic loop whose effect releases the lock holding the contacts, thus triggering breaking if there is a high over current. The response time is very short (around one tenth of a second).
Thermal and magnetic releases, which are generally combined (Thermal magnetic circuit breakers), use an economical, tried and tested technology, but provide less flexibility of adjustment than electronic releases.
Miniature Circuit Breakers (MCB)
- Type B - this model trips between three and five times the rated current (3 to 5 x In). This type is normally used for domestic circuits and small commercial applications where inrush current is non existent to cause it to trip.
- Type C - this model trips between five and ten times the rated current (5 to 10 x in). These MCBs are normally used for commercial applications where there are small to medium motors or fluorescent luminaires and where there is some inrush current that would cause the CB to trip.
- Type D - trips between ten and twenty times the rated current (10 to 20 x In). These MCBs are for specific industrial applications where there are large inrushes of current for industrial motors, x-ray units, welding equipment, etc.
Molded Case Circuit Breaker (MCCB)
- Typically used for system current range from 100 A – 2,500 A
- 1 Pole to 4 poles
- MCCB has IEC, NEMA and ANSI standards
Air Circuit Breaker
Oil Circuit Breaker
Vacuum Circuit Breaker
- Vacuum offers the utmost insulating strength. So it has extreme superior arc quenching properties than any other medium.
- The vacuum circuit breaker has a long life. Unlike Oil Circuit Breaker (OCB) or air blast Circuit Breaker (ABCB), the explosion of VCB is avoided. This enhances the safety of the operating personnel.
- No exhaust of gas to the atmosphere and Noiseless operation.
- The main disadvantage of VCB is that it is uneconomical at voltages exceeding 38 kV.
- Moreover, the VCBs production is uneconomical if produced in small quantities.