MCB & ELCB
The first characteristic is the overload which is intended to prevent the accidental overloading of the cable in a no fault situation. The speed of the MCB tripping will vary with the degree of the overload. This is usually achieved by the use of a thermal device in the MCB. The second characteristic is the magnetic fault protection, which is intended to operate when the fault reaches a predetermined level and to trip the MCB within one tenth of a second. The level of this magnetic trip gives the MCB its type characteristic as follows
MCB its type characteristic
| Type | Tripping Current | Operating Time |
| Type B | 3 To 5 time full load current | 0.04 To 13 Sec |
| Type C | 5 To 10 times full load current | 0.04 To 5 Sec |
| Type D | 10 To 20 times full load current | 0.04 To 3 Sec |
The third characteristic is the short circuit protection, which is intended to protect against heavy faults maybe in thousands of amps caused by short circuit faults. The capability of the MCB to operate under these conditions gives its short circuit rating in Kilo amps (KA). In general for consumer units a 6KA fault level is adequate whereas for industrial boards 10KA fault capabilities or above may be required.
ELCB (Earth Leakage Circuit Breaker):
- ELCB (Earth Leakage Circuit Breaker)
- Phase (line), Neutral and Earth wire connected through ELCB.
- ELCB is working based on Earth leakage current.
- Operating Time of ELCB
- The safest limit of Current which Human Body can withstand is 30ma sec.
- Suppose Human Body Resistance is 500Ω and Voltage to ground is 230 Volt.
- The Body current will be 500/230=460mA.
- Hence ELCB must be operated in 30maSec/460mA = 0.65msec.
Salient Features
