Re: [CAD_CAM_EDM_DRO] 3 phase converter and odd behavior on CNC mill

Measure the incoming line-to-line voltage; should be around 240 VAC.

Measure phase to phase voltages coming out of the converter with the load
off and on.

In general three phase work the phase to neutral/ground voltage doesn't make
a whole lot of difference. The whole idea of three phase power is to hang
the load between phases. Assume it is wired delta until proved differently.

Smell the phase converter; does it have a strange or "burnt" odor? Open it
up and look at the "guts", especially capacitors. Be careful, if there
aren't bleeder resistors some of the capacitors could be charged enough to
hurt someone. Are any of the caps bulged, or showing signs of leakage around
the terminals or seams? Caution, if the phase converter is really old, the
metal can capacitors could contain PCBs. Check the relays inside the phase
converter for burned contacts.

If the controller *electronics* are powered by a single phase (two wires) be
sure they are connected to the two hot wires that go back to the 240 V
supply. If at all possible it is best to avoid running electronics off the
generated phase.

Keith Bowers - Thomasville, NC

----- Original Message -----
From: "writetoalan" <flyspeck1@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, October 11, 2002 4:56 PM
Subject: [CAD_CAM_EDM_DRO] 3 phase converter and odd behavior on CNC mill


>
> A friend of mine recently wanted to show me a part cutting on his CNC
> mill (a BPort) that he had running with a phase converter. The
> machine was behaving very badly when I showed up, however. He said
> that it was running earlier in the day, but when I popped the back to
> look at the voltages I got the following (when referenced to ground):
> 120V, 60V, 60V. This seems *very* wrong to me as I would have
> expected at least two 120V legs (the two from the Power company).
> Anyhow, I am planning to look at the thing before he blows up the
> CNC. My question is pretty simple. The converter is a Cedarburg and
> it has a bunch of wires coming out of it; a "bunch" because I don't
> know if it is a Wye or Delta wound motor. What is the best way of
> determining if a coil is burned out.... and I don't have a megger.
>
> Thanks.
>