Excess current protection unit for electric motor supply cables - has current transformers connected to common relay metering current in multiple wire cables

摘要

Excess current protection unit is for parallel connected multiple wire cables feeding large electric motors. The wires are connected to the respective phase(s) of a multiphase supply mains network having a current transformer in each cable wire. The secondary winding(s) of the current transformer(s) feeds a current metering relay, and the number of metering relays used matches the number of cables, with a relay connected to a current transformer in each case. The arrangement is such that at least two of the current transformers connected to the same relay belong to different cables, the transformers being in different cables, the transformers being in different phase cable lines. Thermally sensitive relays are specif. also arranged in the secondary circuits of the current transformers.