Legrand RCCB DX3 40A 100mA 2 Pole DP 240 V AC applications 4118 57
Official DX3 RCCB (Residual Current Circuit Breaker) Video by Legrand
RCCB and its Uses
A Residual Current Circuit Breaker (RCCB) is used as an important safety measure for the protection of electrical circuits. It is basically a current sensing device that can automatically measure and disconnect the circuit when fault occurs in the connection or the current becomes more than the rated sensitivity. RCCBS are capable of providing real-time protection to circuits and reduces the chances fatal injuries to human beings in case of an accidental touch to the live wire.
The principle behind the working of RCCB is the Kirchhoff’s Law which states that in a given circuit, the incoming current is equal to the outgoing current. RCCB measures the difference in current values between live and neutral wires. In ideal conditions, the current from the live wire should be same as the current through the neutral wire in the circuit. When fault occurs, the neutral wire current is reduced. The differential between the two is called Residual Current. RCCB is triggered to trip off the circuit on spotting a residual current. The residual current device consists of a test circuit for reliability. On pressing the test button, current starts flowing through the test circuit. Due to an imbalance in the neutral coil of the device, the RCCB trips and the supply is discontinued.
Advantages of RCCB
- Protection against earth faults.
- Protection against leakage current.
- Disconnects the circuit automatically when the rated sensitivity is exceeded.
- Can provide dual termination for cable as well as bus-bar connections.
- Protection against voltage fluctuation.
Sensitivity of RCCB
An electric shock of up to 30 mA can be sustained by human beings. A prickling sensation is evoked by up to 10 mA current. When the current exceeds 10 mA, muscular contractions are caused and can lead to a respiratory paralysis on reaching 30 mA. Hence the RCCBS are designed to control small changes in the residual current. They can track high fluctuations in the residual current to the extent of 300 mA for protection against fire.
Classification of RCCB
There are two types of RCCBs: 2 pole type and 4 pole type.
- 2 Pole Type: 2 pole RCCB is used for single phase supply connection consisting of only a live and a neutral wire. There are two ends for both the wires. A rotatory switch is used in ON and OFF positions.
- 4 Pole Type: These are used for three phase supply connection. The three phases and the neutral wire are connected at two ends. The operation is same as 2 Pole RCCB.
Limitation of RCCB
Some of the limitations of RCCBs are:
- RCCBs can operate only on normal supply waveforms and is not suitable when non-standard waveforms are generated by loads.
- Unwanted tripping occurs in RCCBs due to sudden changes in electrical load.
- They cannot provide protection from current overloads. RCCBs are used only when the live and neutral wire current differ.
- No protection against line-neutral shocks.
- No protection from overheating.
- In industries
- In high voltage commercial set ups.
- For many residential applications.