Wired rpc to 600 transformer.......... Issues

windsormw · Oct 27, 2015

Hello Pm

I have a Finch Williams rpc, built it myself and recently wired a 15 kva 240\600 transformer.

The hook up seemed straight forward but perhaps I've over looked something. I wired T1, T2 & T3 from rpc to X1, X2 & X3 on the transformer.

Any suggestions?

windsormw · Oct 27, 2015

It buzzes and will not build rpms

JST · Oct 27, 2015

So, what is the size of the RPC in kVA / HP?

WHAT will not build rpms? The RPC? You do not want a load on the RPC until you have it started up. If you are trying to start it with that in place, it won't work. Connect the transformer after the RPC is going.

windsormw · Oct 27, 2015

It's 10 HP. No machines are on during start up. My rpc has worked fine for years.

Are you saying the transformer is drawing a big enough load to prevent the rpc from starting and closing a set of contacts after start up is the way to solve it?

motion guru · Oct 27, 2015

Start the RPC and allow to come up to speed . . .

Wait 3 - 5 seconds

Close contactor between RPC and transformer (240V) and allow RPC speed to stabilize

Wait 1 second or more

Close contactor to load (600V)

TDegenhart · Oct 27, 2015

A transformer is nothing more than a motor without a load. It draws magnetizing current just like a motor.

Tom

motion guru · Oct 27, 2015

I used a similar setup for several years before we moved into a building with a 400kVA 480V 3-phase service.

We designed a 2 lane log bucking line with 4 positioning conveyors each at 50HP and were able to power this drive cabinet (200HP of drives) and spin motors to rated speed with a 5HP RPC feeding a 15kVA 240:480 transformer . . . we couldn't accelerate the motors very fast but we could run them all and test all of our software all from this dinky little 5HP RPC and transformer combo.

windsormw · Oct 27, 2015

thats exactly what I needed to know ,

Thanks PM , I'll give it a shot as soon as i scare up some more parts .

Scott

JST · Oct 27, 2015

Good. Should work OK then.

One serious issue is that the transformer, if not disconnected, is a load on the STARTING circuit..... And that may be most of the issue here. The start circuit may not be able to function with that transformer loading it un-necessarily.

jim rozen · Oct 28, 2015

Disconnect the starting circuit stuff.

Start the idler with a pony motor, unloaded. Then energize the
idler, then put the transformer online after the idler is up to
speed and the output is stable.

If the idler won't keep running after the pony motor is
removed, somethings wrong with the idler.

If the idler chokes and spins down when the transformer is
put online, there's something wrong with the transformer setup.

t.jones · Nov 21, 2015

Did you get this working ? I'm close and I have some parts. ---Trevor

ErikM · Nov 25, 2015

Scott, I have a 15 hp RPC coupled to a 15 kVA 240:600v autotransformer to run a 10 hp 600v planer.

As note above, I start the RPC in a no load configuration then close the fused disconnect to power up the transformer, and then start the planer. Works like a charm.

Suspect that all you require is a disconnect between the RPC and transformer.

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Wired rpc to 600 transformer.......... Issues

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