Earth-leakage Circuit Breakers (ELCB)




Earth-leakage Circuit Breakers (ELCB)

อุปกรณ์ป้องกันไฟรั่วไฟดูดคุณภาพสูงสามารถป้องกันอันตรายอันเกิดจากไฟฟ้าดูดจากการสัมผัสโลหะเปลือกนอกของเครื่องใช้ไฟฟ้าที่ขัดข้องเมื่อกระแสรั่วเพียง 30mA

An ELCB ((earth leakage circuit breaker) and an RCCB (residual current circuit breaker) both have similar purposes, in that they are intended to trip when the current is not confined to the current carrying conductors. Another name used is current balance circuit breaker. These are all used with grounded power supplies.

The original use was for larger motors and generators/transformers, where the insulation can fail, and the voltage on the frame of the machine can rise dangerously above ground due to the ground resistance and fault current.

An ELCB had a current sensing coil in series with the ground cable, so the supply would be tripped if current occurred in the ground lead. This was often combined with a voltage sensing coil on the frame also, which used a separated ground some distance away.

The RCCB senses the balance of the go and return current in the current carrying conductors and trips the supply if the current is different. The current in the supply cables is different because some is returning via ground. The main purpose is to provide additional protection against electric shock when someone touches an active conductor.

These devices trip with only a few milliamps of current imbalance and within a specified time period, so that in theory the supply is removed before someone contacting active wires can receive a dangerous shock.

These terms have become more or less interchangeable now, in the domestic situation at least, though it could be that a true ELCB is obsolete except for specialised situations.

                How they work and a drawing? The earlier designs used magnetic components, though modern devices may be magnetic (a specialised relay) or electronic. If you search for "How it works RCCD" you should find some simplified diagrams of the magnetic types. The electronic type may use a transformer with a current winding for go and a current winding for return, so the two currents cancel. A third winding detects the voltage produced when they are not balanced. There is no point making your own, as the testing and certification is rigorous if you are required to have them by regulations.

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