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

Terry,

Testing with the megger will not harm the motor. Its purpose is to
see if there is a breakdown in the insulation at high voltage.
Readings coil/coil and coil to frame should be infinity, or very high
(tens of megohms).

Bernard



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "James Owens"
<wotisname@l...> wrote:

> 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