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935-TV motor specs

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petertha

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Sorry to intrude on a PM subforum, but I was curious if someone could reference their PM-935-TV motor plate - specifically the current rating at corresponding 220V single phase. I have a 'different' 935 nominally rated 3HP = 2.2KW which is stamped 20A at 220VAC. Its tripping out 15A breakers on no-load startup & now I think I know why.

Help me understand this. If I divide my watts by line voltage I get something around say 10-12A (I'm in 240V territory). But that must be something like constant current right? Is the added current headroom from that to 20A in my case, to accommodate the capacitor thingy's higher demand spike at the beginning & that's maybe why things go silent? So now that it appears I have a new panel upgrade headache to deal with, should I be providing for say 25A or 30A on the breaker to add headroom to 20A? I'm pretty sure I'm limited to 40A on the entire sub-panel & would prefer not to mill in the dark :/

What sort of line duty vs motor spec current are you folks running?

mill motor specs.jpg
 

mksj

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You are not accounting for efficiency (~60%) and also start-up current which can be very high. FLA of a 3Hp single phase motor ranges from 14-18A based on published values. I believe the breaker size is something like FLA x 125% (so 25A based on the motor's specs) and you round up the breaker size. I would use a 30A breaker with 10AWG wire. Typically you want to have a thermal overload relay or some form of fusing, do not see any guidance in the manual. A breaker protects the wiring, not the motor. There are motor thermal overloads and breakers that protect the motor form overload.
 

petertha

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Thank you, starting to make sense.

I have what I think is an overload thingy on the rear of the mill column. The tech said the 15A panel breaker is probably kicking out long before that.

So sounds like I need to reconfigure panel for 30A and also re-do wires & outlet for 30A because I'm guessing its all 15A duty there too. Poop. That's why I was posting here, I looked through the PM manual & didn't see a recommended line current duty matchup to motor plate specs. That, I'm finding out, is like a super important thing to consider.

IMG_0608.jpg
 
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