Shop Circuit

The Rotary Phase Converter (RPC) I detailed a few posts back is part of a large shop circuit I’ve built.  My circuit takes is 50A 240V single phase and converts it to 240V 3phase and, via a transformer, 480V 3 phase.

The following picture shows my entire circuit.  Power comes in from the left, through the disconnect, and then goes up and around into the control circuit which is the box with the light and buttons.  From there power flows into the breaker box.  The RPC is connected to the lower left hand corner of the breaker box. With the RPC running, the generated third phase is back fed into the breaker box.   Three phase also goes into the other disconnect which is connected to the 480V to 240V transformer.  From here, I have the 480V three phase power I need to power my mill and lathe.


My control circuit starts the RPC and, via a voltage monitor, keeps an eye on the voltages.  If my RPC suddenly shuts of the voltage monitor will cut power to everything to keep from damaging my machines.  Shown below is an electrical diagram of the control circuit.  The voltage monitor takes about 10 seconds to start up in the meantime a bypass timer (ICM175) keeps the RPC running.  After about 15 seconds, the bypass timer shuts off and control of the RPC is given over to the voltage monitor.  Everything works as plan.  One oversight I had was that the bypass timer starts counting down from the instant it gets power.  Unless I cycle power to it, I’m not able to start my RPC.  To fix this I plan to add a normally closed push button to rest the timer.


Once I had my control circuit designed, I measured all the parts and the box to figure out how everything would be laid out.  Eventually I got it all stuffed in the digital box and the wires were drawn in.ControlCircuit2

This is what the actual control circuit looks like.  Pretty much like the diagram above.


I think I posted before, but this is the 3 phase 480V to 240V transformer.  I’ve wired it backwards to convert 240V to 480V.  Transformers are nice in that they work well in both directions.

CS3I’ve found that my circuit works pretty well and provides power as expected.  I tested cutting power to one of the lines going to the voltage monitor and it cut off instantly as planned.  Cool!  I can’t really show you 480V but I plan to give the mill a try soon!


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2 Responses to Shop Circuit

  1. steve says:

    Hi David
    What is the spec of the idler motor that is used?

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