Motor relay is not fooled by "regenerated" phases

The Italian relay-maker Finder has developed a three-phase monitoring relay that protects motors by detecting a loss of phase or incorrect phase rotation. The 72.31 relay is said to provide reliable monitoring of phase losses, even if a lost phase is "regenerated" by the rotating motor — a condition which some monitoring relays detect and thus fail to disconnect the supply, risking damage to the motor. The relay is said to discriminate phase regeneration up to 80% of the line voltage.

The relay ensures that motors are not damaged by phase losses or incorrect rotation. If an error is detected, positive safety logic triggers the contacts to a failsafe open position.

As well as protecting motors in plant and machinery, the relay can help to satisfy mandatory requirements for ensuring that motors in transportable equipment rotate correctly.

The relays, whose outputs contacts are rated at 6A (15A peak), operate from 208-480V three-phase AC supplies. They are 84mm high, 55.5mm deep, and 17.5mm wide, saving panel space.

The motor protection relays, with their built-in electronics, are an example of Finder`s strategy of moving increasingly from basic relays into value-added products.