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Earth-Leakage Circuit Breakers (ELCB)

Earth-Leakage Circuit Breakers

Earth leakage circuit breaker:ELCB is a molded case circuit breaker used in a low voltage AC circuit to provide electrical shock protection and prevent fires from leakage current.
As a general abbreviation, ELCB in our model name is denoted as "NV".


ELCB is defined as a "device with integrated ground fault detector, tripping device and switch mechanism in an insulated body, and automatically shuts off the electric current in the event of a ground fault".

structure of ELCB

To avoid nuisance operation caused by high harmonics or surge

Digital filter

Even with the inverter circuit with digital filter circuit, a part with the sensitivity current as a general circuit can be selected.


Effect of digital filter

DPDC surge discrimination

A DPDC surge discriminating circuit is incorporated. It is judged as a ground fault and the circuit breaker functions only when the ground fault current polarity alternates with the positive/negative poles for a set time. Thus, the circuit breaker operates accurately without incorrectly tripping at a lightning surge, etc.

Operation of DPDC surge discrimination

Necessity of ELCBs

Types of earth leakage circuit breakers

The type AC corresponds to typical alternating current leakage currents. In an electronic circuit such as an inverter or servo, it the rectifying circuit fails, an earth leakage current with a half-wave rectified waveform or a phase-controlled waveform might be generated. In this case, type A earth leakage protection characteristics are needed to detect the half-wave rectified or half-wave phase-controlled earth leakage current waveform.
Then type A leakage protection characteristics is equipped with CE marked and UL489 listed ELCBs up to 250A. (except for NV30-CS)

Operating characteristics at ground fault current

Risk of electric leakage

With 2-3mA passing current, human starts to feel current, but not dangerous even when continued. With 5-30mA passing current, human has trouble breathing or blood pressure rises. Several minutes is the limit. Some 100mA-some A ground fault current causes arc ground fault. Finally it heats and causes the building materials to ignite fires.
ELCB 15mA-30mA high speed type can protect electric shock accident. Also ELCB some 100mA can protect the fires.