Re: [CAD_CAM_EDM_DRO] Re: Phase converter for CNC lathe

In a message dated 4/30/01 8:47:47 PM Eastern Daylight Time,
dougrasmussen@... writes:

> Randy,
>
> Interesting what you say about the European motors. I have an Emco
> Mairer (sp?, I should've learned to spell it by now) CNC lathe which
> I purchased new 14 years ago. My purchase was with the guarantee it
> would run off an Arco phase converter that I already owned. The
> spindle motor is rated around 6 hp. It runs fine most of the time,
> except when our line voltage drops, like around dinner time. Then
> the machine errors out, with a "spindle drive not ready" message,
> which translates to, "shut down for the day and come back tomorrow".
> For whatever reason they set these machines up to be very sensitive
> to incoming voltage, but that sensitivity only affects the spindle
> motor, everything else works in a low voltage condition.
>
> Like other European machines I've seen this one came with a multi-tap
> transformer because it runs on 380V, 3 phase. You can switch the
> transformer leads around to get it to run with most any line voltage
> condition, we've setup for the most common line voltage which is
> fairly steady from morning to late afternoon. Incidently, forget
> about even trying to run on Thanksgiving or Christmas.
>
> Doug
>
>

Doug:

When I was working for SCMI (now called SCM Group USA) we were told by the
motor manufacturers in Italy that the voltage tolerance was +/- 5% whereas
most US motors are at least +/- 10%. Add to that the fact that most of those
European motors are set up for 380 VAC three phase it doesn't take much of a
voltage swing to cause a problem. We were also told that all they do when
they re-rate the voltage on the motor nameplate for the US is to change the
voltage stamped on it and increase the RPM value by approximately 20% due to
the change in operating frequency from 50 Hz to 60 Hz.

We found the motors to be quite reliable but you did need to pay close
attention to the incoming voltage. Another thing you might not know is that
the same holds true for their transformers. We found that transformers rated
for 440 VAC input with a 380 VAC output to the machine would "saturate" at
any voltage above 480 VAC. If you have a nominal incoming line voltage of
440 and it takes a +10% jump you are at 484 VAC and the transformers would
literally quit working until the voltage dropped back down or you put a
buck/boost transformer between the incoming line and the transformer.

Regards,

Randy Abernathy
Woodworking Machine Specialist
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
Phone/Fax: 770-974-5295
E-mail: cnc002@...


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