Relay stops 3-phase motors overheating

E-T-A Circuit Breakers has introduced a PCB-mounting relay designed to prevent three-phase motors from overheating or burning out, by disconnecting all three phases simultaneously.

The E-T-A 3620 relay, which the company claims is "unique", disconnects the phases within 30s of a temperature sensor detecting excessive heat in the motor windings. The relay incorporates a fourth pole which can be used for remote status signalling.

The relay, which has a footprint of just 35mm by 35mm, is rated for auxiliary circuit currents of up to 10A per phase, at 400V AC. It is available in two versions: one has a manual rest button; the other resets itself automatically after a variable delay.