I just bought a 10hp Okuma lathe and I am trying to figure out how to power it in my home shop. I have a free to me 25hp motor I am considering turning into a RPC for this purpose. My only concern is if my 100 amp service will be adequate to run a RPC of this size and will I need a pony motor to start it? Also does anyone have any real world numbers on what a 25hp RPC will pull just idling? Thanks, Aaron
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25hp RPC for 10hp Lathe
- Thread starter aarolar
- Start date
- Replies 13
- Views 1,999
BT Fabrication
Titanium
- Joined
- Nov 3, 2019
- Location
- Ontario Canada
my 20HP is rated at 49.5A at 220V 3 ph. in single phase is about 89A pull. startup can pull about 160A on my 20 in 3ph or about 3X. that can max out about 35KVA, 100A 220V 1ph maxes out 28kva.....
you might be just able to squeak it in. no load startup is much less, it just depends how the lathe turns on.
you might be just able to squeak it in. no load startup is much less, it just depends how the lathe turns on.
johansen
Stainless
- Joined
- Aug 16, 2014
- Location
- silverdale wa
Use an idler to start it an add your power factor offset caps to be nice to your neighbours..(if you have any on the same transformer.
Ive a 30hp transwave rotary running of a 100 amp service thats starts on a 60amp fuse (iirc), zero problems.
Edit: on idle mine draws about 7amps (240v)
Last edited:
jim rozen
Diamond
- Joined
- Feb 26, 2004
- Location
- peekskill, NY
Numbers:
Your 10 HP load motor will draw roughly 7500 watts (750 watts/hp) and at 240 volts single phase, this is approximately 30 amps. Figure the efficiency is not 100 percent so maybe 40 amps if you run the Okuma full bore. Which you probably won't. The idler will probably draw at most 5 hp or so, so a 50 amp breaker will be more than enough. Start the idler with a pony motor to reduce the inrush. I think the 100 amp service should work.
Your 10 HP load motor will draw roughly 7500 watts (750 watts/hp) and at 240 volts single phase, this is approximately 30 amps. Figure the efficiency is not 100 percent so maybe 40 amps if you run the Okuma full bore. Which you probably won't. The idler will probably draw at most 5 hp or so, so a 50 amp breaker will be more than enough. Start the idler with a pony motor to reduce the inrush. I think the 100 amp service should work.
duckfarmer27
Stainless
- Joined
- Nov 4, 2005
- Location
- Upstate NY
Aarolar -
Like Jim said, should work as long as you use an pony motor to start it. I have a 20 HP ARCO Roto Phase and start it off the capacitor bank. I have to feed that with a 100 amp breaker. One other thing to consider when starting something that large is the effect on the incoming line / transformer. Out house is on a branch 'end of the line' transformer. Shop is in s separate building and service from the house, but off the same transformer. My wife always knows when I fire up the RPC as the lights 'blip'. If I had a neighbor who did not like that it might be troublesome - luckily my wife just kids me about it.
Dale
Like Jim said, should work as long as you use an pony motor to start it. I have a 20 HP ARCO Roto Phase and start it off the capacitor bank. I have to feed that with a 100 amp breaker. One other thing to consider when starting something that large is the effect on the incoming line / transformer. Out house is on a branch 'end of the line' transformer. Shop is in s separate building and service from the house, but off the same transformer. My wife always knows when I fire up the RPC as the lights 'blip'. If I had a neighbor who did not like that it might be troublesome - luckily my wife just kids me about it.
Dale
T-Man 1066
Aluminum
- Joined
- Jul 21, 2019
- Location
- N. Illinois
I just set up a 25 HP RPC. On a 30 amp breaker it would trip maybe 1 out of 10 startups. No load idling I pull 9 amps. I have it going into a 30 KVA transformer, wired in reverse to step up the voltage. With the transformer in line, It trips maybe 1 out of 3 startups, but when idling under no load it pulls around 27 amps. I did have it running my Wilton radial arm drill, still on the 30 amp circuit, no problem. Small motors on the RAD, 5 hp. I am going to step up to a 100 amp infeed, and try running a 3H-48 Devlieg on it.
EmGo
Diamond
- Joined
- Apr 14, 2018
You have a #3 Devlieg at home ? Color me impressed
When I was stuck for a while without 3 phase, just used a rope pull on the ol' 3 ph motor converter. Cheap and dirty.
Thanks for all the input guys I am going to attempt to rig up something quick and dirty to test proof of concept this weekend. When using a pony motor I will only need capicators to level the lines out correct, I've seen several you tube videos of guys running straight off a motor with no caps.
T-Man 1066
Aluminum
- Joined
- Jul 21, 2019
- Location
- N. Illinois
You have a #3 Devlieg at home ? Color me impressed
When I was stuck for a while without 3 phase, just used a rope pull on the ol' 3 ph motor converter. Cheap and dirty.
Yessir... 14 tons of fun!
neilho
Titanium
- Joined
- Mar 23, 2006
- Location
- Vershire, Vermont
It works, but under load, thermals trip because of the current imbalances.
The whole plan fell apart, when I pulled the cover off the pecker head it only had a single set of taps. Turns out the motor was rewound at some point and was only rewound single voltage, considering where the motor came from I'm 99% sure it is high voltage. The plan now is to pull the 10hp from the lathe and use it as a RPC to run the 5hp I have hopefully it'll have enough grunt for my purposes.
neilho
Titanium
- Joined
- Mar 23, 2006
- Location
- Vershire, Vermont
10hp should be more than enough to run 5 hp, esp if you use run caps.
I use a 25hp RPC at home, originally to power a 10hp Mazak turning center though now it powers a couple of BOSS mills and my WEBB lathe with a 7.5hp motor. It's on a 50amp breaker that I've never tripped. I start it with an old 3/8" corded drill. I do have the parts to put a pony motor on it but haven't gotten around to it yet.
