ROTARY PHASE CONVERTER WITH TWO IDLER MOTORS ?

As Brian says, the 10 HP RPC may be just fine. I have a 5HP RPC and it works fine to run my 5HP air compressor, but it doesn't like starting my lathe on the 5HP setting (2 speed motor, so I usually run it at the lower speed, which is 3HP). You have a clutch, it will probably be fine.

The 575V is an issue. I am running 3 different 575V machines. I'm simply running a 230 to 575 three phase transformer. It was originally sold for step down service, but it works the same to go the other way. I seem to loose capability through the transformer, as the 3HP mill motor does not like to start on the higher speed. Not really an issue as the motor controls are set up such that I can start on the low speed, then punch the high speed button and it comes right up.

As Brian said, put in a little smaller motor, 5HP or 7.5HP, whatever comes your way - tell us about this new machine.
 
I wouldn't put a motor any smaller than 10 HP on the Lodge & Shipley lathe Brian has. It's not a big problem on start up, but it is trying to get it into the higher spindle RPM's. I ran my L & S on the 10 HP motor that it came with on a shop built static phase converter. Had it balanced with oil filled capacitors on the generated leg along with the other two, too. I'm sure some of the loss power had to do with not having full 3-phase power. Using the static converter, I had a bank of four 375-450 mFd capacitors in parallel providing juice for startup. And it took every bit of it, too. Of course, the old 1950's 10 HP frame motor on that lathe would be like a 30 HP motor today!

If I remember correct, the motor pulley is about 8" in diameter with 5 or 6 "B" section grooves and the pulley on the input shaft is about12" OD. That much belting takes a lot of power to get it up to 1800 RPM on the motor. So a 5 HP pony motor may not be large enough. 7-1/2 HP, maybe.

Ken
 
I am late in getting back to reply, but Ken has described my lathe. As he said, it is a Lodge and Shipley 16" (really 18" ) swing and 8' between centers and weighs in at around 9000 lbs. I have started a thread on the L&S forum. I agree with Ken, about keeping the 10hp motor capability. I like to keep things as original as possible.

So, as I am intent on keeping the 10hp capacity, can anyone guide me to a schematics diagram dealing with a 10hp and a 5hp combination RPC set up ? I have done some digging, but haven't found anything conclusive so far. As well, I don't trust my limited knowledge.

Brian
 
Hey Karl, so I read the thread, and watched the video. You start the 5hp to make the 3 phase power to start the 15hp then they both run together, is that right? Are you using start caps to start the 5hp? Do the 2 motors share run caps?

I had to re read my own thread. First tried to get away with no start caps (just run caps only, brought in at startup) and that did not work out.

Motor 1 comes in with start caps. these caps drop out on a timer after one second.

Motor two comes in at about three seconds. The system runs real ruff until the run caps for the entire system come in at about five seconds.

watch the video, you cans see the second motor come in, then smooth out. there's a quick shot of volt meters showing great balance.


I had wanted my son to put a loose pulley and belt between the two motors. if this was done, I think you would never even see motor 2 come in. And you would not need the delay timer for the run caps, just bring them in with motor 2
 
So, as I am intent on keeping the 10hp capacity, can anyone guide me to a schematics diagram dealing with a 10hp and a 5hp combination RPC set up ? I have done some digging, but haven't found anything conclusive so far. As well, I don't trust my limited knowledge.

Brian

If I understand correctly you have a 10 HP converter running already...

I also have a big lathe, a Mazak M4 (machine weighs 16,000 lb has a 22" swing by 72" long). I learned that you need considerably more total HP in the RPC than the lathe motor if you want to keep any decent starting load and voltage balance..

Anyway, I'd use the 10 HP to build from. Add a second motor making the RPC total HP near twice what your lathe motor is. All you need is a motor, delay timer relay and motor starter. Personally, I'd suggest a loose belt between these two motors so motor 1 spins motor 2 up. If this is done, I'm almost positive you could bring in your balancing run caps along with motor 2.

The amount of run caps has to be done by trial and error; build your caps box with plenty extra installed and make it easy to add/remove run cap connections. Permanent voltmeters are cheap make balancing trivial.

I'll be glad to help with the wiring step by step when you get there. For now, get yourself a big electrical enclosure, a large used 3 phase motor, a motor contactor, a delay timer and about 70MFD of run caps per total HP of your system. if you don't belt the motors, get a second delay timer and motor contactor.

Extra bonus: I found 3 phase load centers are cheap in ebay. One of these makes it great to fuse each component and make future equipment additions easy.

EDIT ON 2017 11 07 There is a typo above. get about 20 MFD run caps per hp in your converter
 
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Hi Karl,,
Yes, I already have a 10hp RPC up and running. Based upon what you wrote, should I be looking for another 10hp motor for a total of 20hp in the RPC ? Or is an additional 5hp enough ?

WNY Phase Converter sells a complete 20hp RPC panel for $300.00 USD shipped. Would this be another avenue?

Brian
 
You are going to get differing opinions on if 15 hp is enough. More HP here will improve voltage balance and starting load on big motors. But you can try what you have, if you want.

that's a complete 5hp converter, correct? its worth more than just a surplus 10hp motor. You need to find a surplus motor jockey, ask around, they exist.

that 20 hp panel leaves you looking for a 20 hp motor. And starting 20 hp will really dim all the lights on your place if you have the typical home 200 amp service.
 
Hi Karl,

Yes, the 5hp motor is a complete RPC unit that I bought from Elimia converters in Kentucky. My residential service is the typical 200 amp service.

Brian
 
I don't know anything about your lathe, I will say that my 16" (really 18" swing) Monarch runs well with a 5 hp motor. Could it do better with a 7-1/2 or 10hp motor? Yes, most likely but I wouldn't test it and the 5hp does well enough.

I'm convinced that your current 10hp RPC can run your lathe just fine, even if you replace your current high voltage motor with a 10hp 240V 3 phase one. In the event that you do have any issues starting your lathe with the 10hp RPC then just start another machine on the circuit first. The HP of the RPC plus the HP of the second machine will allow you to start your 10hp lathe.

Here is Keith Rucker talking about his RPC system

 
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