RE: [CAD_CAM_EDM_DRO] Re: VFD drive problems with older 3 phase motor?

I may have joined this thread somewhat late and missed sections.

However, for what it's worth many VFD units have an 'enable' input
no matter what settings you have, nothing works till this is taken high
or low (see makers VFD spec) - caught me out a few times in the past.

Merry Xmas to all

Dave Fisher UK

-----Original Message-----
From: Jon Elson [mailto:elson@...]
Sent: 26 December 2003 16:18
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: VFD drive problems with older 3 phase
motor?




Ted Inoue wrote:

>aha! What you describe is almost exactly what I have measured. Your
>diagram is the same as what I've drawn.
>
>The VFD drive I'm using is a TECO-Westinghouse FM100 driver. 1 phase,
>220V input, 3-phase output. The default settings of the drive seem
>reasonable, but there are so many that I'm not sure if I'm missing
>something in there. What are the key settings besides accel/decel and
>HP that I might need for basics? Also note - the unit doesn't appear
>to be tripping out or any such thing. From the display panel, the
>drive seems happy.
>
>

The drive seems happy, but the motor does absolutely nothing? VERY
odd. Usually, you can also program several points on the volts/Hz line.
Many drives have a minimum starting Hz point, like 1 Hz, and a minimum
voltage for it, like 10 V, then a midpoint, such as 125 V @ 30 Hz, and 240 V
@ 60 Hz for the upper end.

>The motor plate indicates that it's a 220V motor. No option on the
>plate for 440V. But it is indeed a dual-speed unit.
>
>Before I pull the motor apart and rewire the windings, I'm going to
>try running it with the rotary converter I've got and ensure that
>everything works in its original configuration.
>
>

You can just give the motor a good spin by hand and then plug any 2 of
the phase wires in to 240 V power. If it hums loudly and stops, something
is wrong with the wiring or motor. If it accelerates slowly to
operating speed
(1 - 2 seconds) then you have it right. (It will accelerate faster with
proper
voltages on all 3 phases.)

>A question on winding resistance/impedance. Currently I'm measuring
>about 0.7 ohms for the windings. Is this typical? It seems really low!
>Especially if I rewire and get 1/4 the resistance. But I've not worked
>with motors of this size before.
>
>

Low? Actually you are measuring the resistance of your meter's test leads.
Put them together and find out what the "zero" is, usually anywhere between
zero and one Ohm. Subtract that from the unknown reading to get a better
idea of the true value. You are measuring the DC resistance of the motor's
wire, that's all. The inductance and back-EMF of the motor, when running,
increase this value dramatically.

Jon



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