ECN Forum Forums General Topics of the Trade General Discussion Area motor starter heater ratchet thingy

On a square D motor starter. What's the function of those ratchet wheels on the side of the heaters?

A mechanical function of the 'trip' mechanism that "opens" the contacts on overload seems to come to mind.

John

One heater melts and breaks and the "trip" pawl is released opening up the other two poles. I get that. But why a ratchet wheel? It doesnt seem to turn...or does it turn when it overheats?

Yes, it turns when it gets hot. There is a low melting point metal around the gear shaft and when it melts it lets the gear turn and that in turn opens the overload relay contact.
Don