Earthing monitor for portable electric generator - uses current differential earth leakage circuit breaker to monitor earthing abnormalities in auxiliary earth wire linked installation

摘要

The device provides an auxiliary earth circuit which opens the circuit breakers (14) feeding each outlet when the earth circuit is incomplete. A differential earth leakage circuit breaker (8) in the generator output line senses the earth circuit abnormality. Where motor loads (2) are used the outlet contact (14) operating coils (15) are fed through the thermal protection (3) of the motor. A voltage step down transformer (4) is supplied from one phase of the generator through the differential circuit breaker (8) and its low voltage side supplies the contactor operating coils (15) through the motor frames and a supplementary earth tie conductor (1). A break in the earth path leads to current imbalance in the differential circuit breaker which opens the generator output circuit and isolates the outputs.