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Joined: Dec 2001
Posts: 300
On a square D motor starter. What's the function of those ratchet wheels on the side of the heaters?

Joined: Apr 2002
Posts: 7,313
Likes: 7
A mechanical function of the 'trip' mechanism that "opens" the contacts on overload seems to come to mind.


Joined: Dec 2001
Posts: 300
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?

Joined: Nov 2000
Posts: 2,148
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.


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