Re: VFD drive problems with older 3-phase motors (corre...

Randy, this is not true. Perhaps you are getting confused by dual
voltage windings that use wye or delta connections? If two motors are
similar and one is wye wound and the other delta wound, the winding
measurements would be similar. Even if it was true that the wye wound
was twice the resistance of the delta wound, how could you tell which
you had without something to compare it to? Twice what resistance?
For Ted's issue it doesn't really matter. I just thought I would
point out that you really can't tell the winding configuration from
ohm-meter measurements.

Ted, I agree with you on the phasing. With 3 leads, you can't get it
wrong. All you can do is change the rotation direction. Have you
determined the way the motor was initially wired to the contactors to
confirm your theory of the winding configuration? Did you check all
of the VFD parameters and make sure they agree with the motor
specifications? The only problems I'm aware of regarding running
older motors from a VFD have to due with longevity. For example,
winding insulation breaking down, etc..

~petev

--- In CAD_CAM_EDM_DRO@yahoogroups.com, cnc002@a... wrote:
> In a message dated 12/25/2003 5:52:03 PM Eastern Standard Time,
> pete@v... writes:
> Ted, how was the motor originally connected to the contactors? How
> could you possibly determine wye/delta from ohm-meter measurements
> when wye and delta circuits are electrically equivalent?
> Actually, the resistance measurements for wye connection would be
approx.
> double that of a delta connection within the motor. If the motor's
internal
> connection, or winding connection via and external terminal block,
etc., is a
> delta delta which is two delta configurations in parallel then the
single wye
> would be 4 times that of the delta delta.
>
> Now, to figure out the correct "phasing" connections of the
internal windings
> is a bit more complicated and requires the use of a voltmeter and a
6 or 12
> volt battery.
>
> Randy Abernathy
>
>
> [Non-text portions of this message have been removed]