Re: VFD drive problems with older 3 phase motor?

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 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.

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.

Thanks to all for the feedback. I think I can try a few more tests now
and hopefully get things spinning with power.

-Ted


--- In CAD_CAM_EDM_DRO@yahoogroups.com, Robin Szemeti <list@r...>
wrote:

>
> I'll take an educated guess and say that what you have there is a '2

speed'

> wound motor.
>
> it had 2 speed settings, low (which you already tried) is power to

1,2,3 ..

> 4,5,6 are left floating. This is a 'delta' configuration, the

points 4,5,6

> are centre taps on each coil,
>
> so the three coils are 1(4)2, 2(6)3 and 3(5)1
>
> asci art follows :)
>
> 1
> / \
> 4 5
> / \
> 2---6---3
>
> and ... high speed is still power to 1,2,3, but 4,5,6 tied together

to make a

> 'star' configuration ... try that .. you'll find it does at least

spin, but

> you will still be down on power. (you can also see why connecting

power to

> 4,5,6 effectively cancelled itself out and the motor just whines ...

)

>
> to actually get your motor to work properly with your VFD you will

need to do

> some re-wiring to parallel the windings that are currently in series

on each

> leg of the delta.
>
> take the leg 1-2 that has its centre-tap as 4 ... lets call it

1-4-2 ok? ..

> 4 is actually 2 connections .. so it goes 1-4a,4b-2 ... ok? you

need to wire

> it to take the 1-4a coil in parallel to the 4b-2 coil, rather than

in series

> as they are now. If you are lucky, you'll find that the 4 terminal

in the

> motor block has 2 wires under it ... its then just a question of

labelling

> everything up, confirming with a meter and doing the same for the

other two

> legs. What you should end up with is 3 terminals that hav 1/4 the

impedance

> of 1,2,3 at the moment ... and full power from the motor ...
>
> I've done this on 2 machines now and both run without a hitch ...
>
>
> Without actually seeing the motor its hard to say, but it was a

fairly common

> motor configuration, if its labelled 415 volts the modification I

described

> will make it work fullpower on a VFD from a 240V supply .. scale

those

> voltages to your local mains voltage.
> --
> Redpoint Consulting Limited
>
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