Pony motor RPC starting question

MrWhoopee said:
It's not even necessary to get it up to speed, just spinning is enough. As I said, I knew a guy who started his with a belt (the kind you wear) every morning. Just a 3 phase motor and a disconnect. Wrap the belt around the shaft, pull the belt and flip the disconnect on.
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Wrap the belt around the RPC shaft in the opposite direction, and all of his machines would turn in reverse ;)
 
MrWhoopee said:
It's not even necessary to get it up to speed, just spinning is enough. As I said, I knew a guy who started his with a belt (the kind you wear) every morning. Just a 3 phase motor and a disconnect. Wrap the belt around the shaft, pull the belt and flip the disconnect on.
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Very true. I spin my 15HP RPC up to speed with a pony motor before closing the main relay, that drops the starting current to around running current and my lights don't even flicker. My shop is supplied from a 50 Amp breaker so I have to be careful of starting current on motors.

I installed a 20HP unit for a customer, no pony motor, and his lights dim for a couple seconds on start up with a 200 Amp main supply. Was a bit frightening the first time I started it. :eek:
 
JimDawson said:
I installed a 20HP unit for a customer, no pony motor, and his lights dim for a couple seconds on start up with a 200 Amp main supply. Was a bit frightening the first time I started it. :eek:
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Mine's a 20HP capacitive start RPC. I used a Fluke ammeter on peak current, it showed 209 peak RMS amps on the 200A single phase service. No noticeable light dimming. IIRC, settled down to 9A idle. I'm considering some enhancements as I re-install that in the new shop.
 
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rabler said:
Mine's a 20HP capacitive start RPC. I used a Fluke ammeter on peak current, it showed 209 peak RMS amps on the 200A single phase service. No noticeable light dimming. IIRC, settled down to 9A idle. I'm considering some enhancements as I re-install that in the new shop.
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Is that 9amp idle with balance caps?
 
Barncat said:
Is that 9amp idle with balance caps?
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Yes, that is my recollection. I'm not sure how much of that is reactive load (i.e., what power factor). An unloaded motor tends to run with a fair amount of reactive power, that is, the voltage and amperage are out of phase.
 
Thanks everyone. I got it going over the weekend. I kept popping the breaker until I realized I had power coming off L1 for the start to the coil and from T2 for the latch on of the contactor coil. Once I switched it to T1 for the latch and got it going fast enough it took off. I did have to get it spinning fairly fast so it wouldn’t trip the breaker, but that may be because it is a 25 hp and draws a decent amount at start up. I just need to get some balance caps added in now.
 
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