RPC Question

[Sal Kurban]

Hi all,
I recently purchased a 20 HP rotary phase converter. It is a TEMCO 6500-15kw model to be exact. It is supposed to be a plug-n-play in that it is prewired on a rolling cart with rubber wheels and feet. When I plug it into my 50 amp welder outlet, it trips the breaker with no humming no noise nothing. I looked at the wiring diagram, tested the lines etc and everything seems to be OK. the RPC had been sitting there for few years unused. What else can I check?
Thanks,
Sal.

[Matt Day]

Have you called the manufacturer, or the distributor? If you got it from Factorymation they have excellent CS.

[Bruce Wrenn]

What does the name plate list as "amp" draw.

[Scott T Smith]

Sal, I would check three things. First, I would make sure that the shaft spins freely. Second, I would double check that the wiring is correct regarding the ground wire connection (if a ground and hot wire are reversed it will trip the breaker immediately). Third, I would check with the manufacturer to find out what the start up surge current requirements are.

As an FYI, my 30 HP RPC is on a 100A circuit.

[Sal Kurban]

Thank you all for the input and suggestions. I called Temco and they were very helpful; we figured it was a wiring issue. There was a short circuit and that was tipping the breaker.
Sal.

[Rick Fisher]

Interesting post.. Can a 20hp RPC run off a 50amp breaker ? Not really sure how that works.. What level of performance would you get ?

I have a 20hp PP and its wired to a 100amp breaker and can handle 125.. I always thought a rotary needed a breaker size .. ( never owned a rotary ) ..

[Peter Quinn]

My ten horse runs on as little as 30 amps or as much as 50A, I have it powered on 40A to run multiple machines in series. Did manufacturer give you suggested breaker size? I'm thinking it might spin on 50 and start smaller motors but not likely to give you 20hp on 50a 220v.

[Stephen Cherry]

I have a phase converter with a 15 hp idler motor. I guess that makes it able to run a 10 hp load? Anyway, I run it on a 30 amp breaker, which it has tripped while running my 5 hp shaper.

Be careful with running on 40-50 amp circuits- you want to really make sure the wiring is up to it.

[jack forsberg]

amps have nothing to do with the idlers size other than cranking it over to get it started and the largest motor in the shop it needs to start. What i mean is i have a 10 hp idlers wired to 100amps. How it works is the full load amps on the idlier is what the rotory will start less the currant it takes ups spinning (about 2 apms). so a 10 hp RPC can start a 10 hp motor if caps are set for that. RPC are sized to the largest motor to start. hard start motors like an air compressed need 2 times hp for idlers were as light machines like TS don't. A good rule is 1/3 more for balance .Once other machine come on line and are running on the system they in turn feed the system there unused amps(there become rpcs) and so a 10 hp idlers can run up to 30 hp. You don't get this for free though for every amp of 3 phase you need 1.734 amps of single. doing a load test is in order to fugurr the single phase feed and wire size for the system. so you can feed a larger RPC any thing up to it full load x3 and this will be your out put. and your largest motor

was that as clear as mud.

PP on the other had does not benofit from the othere machine in the system and need to be sized for total load. so a 20hp PP will only run 20HP mind you very cleanly. In the end motors are dumb and you would be surprised what can make them run.

[Sal Kurban]

My ten horse runs on as little as 30 amps or as much as 50A, I have it powered on 40A to run multiple machines in series. Did manufacturer give you suggested breaker size? I'm thinking it might spin on 50 and start smaller motors but not likely to give you 20hp on 50a 220v.

Temco suggested that the 20 HP RPC should be wired to a 50-75 amp breaker. They would not divulge anything on the wire size as that would be up to the local code per their policy.
Sal.

[Duane Meadows]

Well, the math for 20HP at 240 says a little over 62A. I f you are going to run it near capacity, I'd go 70A circuit minimum. That would need at least 4Ga wire.

[Sal Kurban]

Well, the math for 20HP at 240 says a little over 62A. I f you are going to run it near capacity, I'd go 70A circuit minimum. That would need at least 4Ga wire.
Thanks,
I will make sure to upgrade the breaker and the wire...
Sal.