Re: [CAD_CAM_EDM_DRO] Stepper Motor (was: Harrison Lathe and Gecko's)

Hi Jan,

I had already done what you describe to get the 0.4 ohms. What I wanted to
test was the insulation of the windings and didn't know if, using a high
voltage insulation tester (yes mine is a mega), will damage the motor in any
way? This is normally done, where a motor is suspected of over heating or in
my case I don't know the history of it, by putting one probe on a wire/coil
and the casing and then doing the other coil. Any breakdown in the
insulation shows up as leakage.

Regards,

Terry

> > I want to check my Z axis stepper motor. Is it wise to do the insulation
> > test with a mega?
> >
> > The resistance readings are 0.4 ohms across either pair of wires, there

are

> > four coming out of the motor. Which is twice what the manufacturer

quotes

> > for a single coil, so they must be wired in series inside?
> >
>
> Terry: A "megger" is a kind of ohmmeter that measures VERY high

resistances

> in the huyndreds (or more) MEGOHMS range. For steppers, the resistances

are

> generally less than ONE ohm to only a few ohms for some "higher voltage"
> types.
>
> You should have "infinite" resistance between each winding! If you read

0.2

> ohm between 1 and 2, and also between 3 and 4, there should be infinite R
> between 1 and 3 or 1 and 4, or 2 and 3 or 2 and 4. If you read 0.4

between,

> say, 1 and 4, there would be ZERO ohms between 2 and 3, indicating a

"short"

> internally, between 2 and 3. Try again, noting the R between EACH pair of
> wires, and try to SKETCH a diagram to help you visualize this!
>
> Lotsa luck! Jan Rowland