Re: Re: Re: DC versus 3 Phase

On 20 Feb, CAD_CAM_EDM_DRO@yahoogroups.com wrote:

> From: Greg Jackson <jackson@...>
> Subject: Re: Re: DC versus 3 Phase
>
> I was wondering about VFD's and asian motors.

I guess I wasn't making myself clear .. sorry.

My machine came stock with 110V single phase Chinese motors and I
replaced them with American 3phase motors and a VFD. My point was that
the Chinese 3/4HP rated motors were definitely more powerful than the
1/2HP American motors - that the power rating was NOT the exaggeration
one normally expects of an Asian motor.

I do agree that the VFD has a lot of RF hash .. A LOT.

Here's how much. I initially routed the 110 v power line into my
machine, to a power switch, and then back out to the VFD. Tied
together with cable ties was a SHIELDED line with four wires running
to a stepper motor.

When the VFD was turned on, the stepper would "jitter"! Surprising,
especially considering that THE STEPPERS WERE NOT POWERED ! This was
not noise being fed back into the controller and causing spurious
steps, it was energy induced from the 110V line into motor leads.

Currently, everything's in a shielded box with all shielded cables
running everywhere and a BIG FAT noise supressor on the input. Power
switched remotely via a relay.


However, this is the first I've heard of windings melting down, though,
from RF produced by VFDs...

Alan

--

Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta