Full form of RCCB – The full form of RCCB is Residual Current Circuit Breaker.

What is RCCB – Definition of RCCB is given below –

Definition –

RCCB is a device that is used in electrical circuit that trips circuit when current becomes imbalance between phases & neutral. This imbalance may be due to any reason either by touching live wire by a person or due to imbalance load between phases etc. It is also called current operated ELCB.

Working principle of RCCB –

It consists of a sensing coil, fixed & moving contacts. The inside RCCB the phase & neutral wires are wound on main coil. Also a sensing coil is also wound on this coil. The function of sensing coil is to detect the emf induced in the main coil. In case of single phase load, same current flows in both phase & neutral, hence same emfs are induced in the main coil by phase & neutral wire are in opposite direction  so no resultant emf is induced in the main coil.

When an earth fault occurs in the equipment, current in phase wire will not be same in neutral wire as some part of current flows as a leakage current. So, due to this difference current in phase & neutral wire, a resultant emf is induced in the coil which is sensed by the sensing coil which actuates the tripping mechanism & trips the circuit.

SELECTION OF RCCB –

• It should be capable to carry the rated current of load,
• Check RCCB is required for single phase or 3 phase load.
• Check number of poles – DP & 4P where

DP = Double Pole which means phase & neutral wires will be connected,

4P = Fore pole which means 3 phases & a neutral will be connected.

• Fault current rating (in mA) on which relay should trip/interrupts the faulty circuit e.g. 30mA, 100mA & 300mA.

Ex – 40A DP RCCB with 30mA fault current.

LEAKAGE CURRENT RATING OF RCCBs–

30mA DP –

A typical range of single phase – RCCB – 6A, 10A, 16A, 20A, 25A, 32A, 40A, 63A.

100mA DP –

A typical range of single phase – RCCB – 6A, 10A, 16A, 20A, 25A, 32A, 40A, 63A.

300mA DP –

A typical range of single phase – RCCB – 16A, 20A, 25A, 32A, 40A, 63A.

30mA 4P –

A typical range of Three phase – RCCB – 6A, 10A, 16A, 20A, 25A, 32A, 40A, 63A.

100mA 4P –

A typical range of Three phase – RCCB – 16A, 25A, 32A, 40A, 63A.

300mA 4P –

A typical range of Three phase – RCCB – 16A, 25A, 32A, 40A, 63A.

Frequently Asked Questions (FAQs) on RCCB –

Q1) What is the difference between ELCB & RCCB.

Ans) Both ELCB & RCCB provide protection against earth fault/leakages in electrical system by isolating faulty equipment/circuit, but working principle of both is different. Working principle of RCCB is given in above sections while working principle of ELCB is given in separate section of this website.

Q2) What is RCCB circuit breaker?

Ans) RCCB is a circuit breaker that isolates equipment or circuit when earth fault occurs in it. It protects user from electric shock by isolating faulty equipment/circuit.

Q3) What is RCCB Switch?

Ans) RCCB is a circuit breaker that isolates equipment or circuit when earth fault occurs in it. It protects user from electric shock. It protects user from electric shock by isolating faulty equipment/circuit.

Q4) Why RCCB trips?

Ans) RCCB trips when earth fault occurs in the equipment/circuit. On earth fault the metallic body of the equipment gets charged, the RCCB senses the fault & trips. It means, RCCB disconnects the supply to the faulty circuit so that user doesn’t get electric shock. In such situation, fault should be located & rectified as soon as possible then RCCB could be switched on again. (Note- Detailed working principle of RCCB is given in above sections).

Q5) What is function of RCCB?

Ans) The main function of RCCB is to protect a user from electric shock when earth fault occurs in the equipment.

Q6) What is the difference between RCCB & MCB?

Ans) The main difference is – RCCB provides protection against earth fault while MCB provides protection against overloading & short circuit. Working detail of RCCB is given in above sections while working of MCB is given in a separate section of this website.