Phase converters vs. single phase

jmartin · Jan 16, 2007

The only 3 phase item in my old mill and lathe are the spindle motors. I run them on single phase power with no phase converter. I just hold down a push button switch as I turn them on. This momentarily connects a start capacitor to the third leg.

Is anyone else doing that?
Have there been any problems?

I even run my Bridgeport Boss 6 CNC that way.

SamH · Jan 17, 2007

That is about the same as a static converter. It works, but it is not the best thing for the motor, since you are only powereing 2/3 of the motor. In turn, you also don't get total horsepower out of the motor. I don't know if i would risk running a cnc like that though.

peterh5322 · Jan 17, 2007

In general, a Y-wound motor is limited to 2/3 of nameplate HP, while a ∆-wound motor is limited to 1/3 of nameplate HP.

If an external source of leading VARs can be provided, say, using appropriately sized run capacitors, you can more closely approach those limits.

With an RPC, you can equal the nameplate HP.

jmartin · Jan 17, 2007

Thanks for the responses.

I have not had any problems with lack of horsepower in the mill or lathe. I guess I don't really work them very hard or very long.

I don't work the CNC hard either since I mostly cut photographic images into wood. However I do run it a lot of hours since those images are detailed enough to require up to 10 hours of run time.

So far, so good.

Jim

jmartin · Jan 17, 2007

Just for fun, here are some of the images I have machined into wood. Some have a "frame" machined into the board, around the image.

The machined image is somewhat 3 dimensional. I paint it to eliminate the wood grain and to enhance the contrast of the image.

Jim

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