Need Help!- RPC measures 250 volts into my mill?

[CATCH22]

My RPC is putting out 250 volts going into my cnc mill that the spindle motor is rated at 230 volts is this too much voltage and how can I bring it down to 230v if so. I also plan on running a vfd on this mill eventually.

Thanks Mike

[Al_The_Man]

The two 1 phase legs will be 240, the generated phase will usually measure high on a RPC when off load, when loaded it will usually drop.
That much is nothing to worry about.
Al.

[CATCH22]

Thanks Al,
I was wondering do you think it would be better to just run single phase to the vfd and just skip the rpc,I would think it would be cheaper on the electrical bill not having to run a 10hp motor for the rpc.

Thanks Mike

[John Bennett]

Are you using the VFD to get 3 phase power output? If yes, then, just run the VFD (less noise). If you are planning to use the VFD for speed control, then you would run the RPC and the VFD , or look into the control and work of the single phase required and just use the VFD for spindle. You will have to look into wiring diagram as some CNC's have the coolant pump and hydraulic pumps running 3 phase motors.

[CATCH22]

I am planning on using the vfd for speed control but Im pretty sure that the spindle motor is the only thing that will be 3 phase,so can I us it to convert to 3 phase and as a speed control also?

Thanks Mike

[Al_The_Man]

I would go the VFD route, especially if it is the only three phase motor.
The VFD does give you speed control and if it is a 4 pole motor, you can usually safely go up to 160hz.
Al.

[CATCH22]

It was brought to my attention that I should put what I am using this on so here goes.
The mill is an Excello 604 CNC with 3hp spindle motor and that is the only thing that is 3 phase on the mill everything else is single phase power,the vfd I have is an Allen Bradley 7.5hp, I plan on using a breakout board just not to sure what to go with yet. I have viper 200 drives for my servos, and us digital encoders. Sorry I should have posted this before but I was at work and in a bit of a hurry. Thanks to everyone so far for all your input.

Thanks Mike