[ARC5] [Milsurplus] ART-13 dynamotor woes

[J. Forster]

Meir,

The situation is complicated. The dyno is a compound wound machine from
the prints I have of another maker's unit. It has BOTH a series and a
shunt field.

I think you have to Ohm the fields out very carefully and see which coils,
if any, are actually shorted (or open)

One possible explaination for your symptoms would be an OPEN shunt ield.

Best,

-John

===================


> Folks,
>
>
>
> I have an interesting but aggravating problem with a DY-17A/ART-13 Eicor
> manufactured dynamotor. The dyno, by the way is a late WW2 production, it
> is
> in pristine cosmetic condition inside and out and it was never used before
> I
> got it recently. After 3 weeks of running my ART-13 with it for a couple
> of
> hours a week, in the middle of a  CW net it started to smell like hot
> insulation. I shut it down and troubleshooting indicated that there is a
> short to ground somewhere in the field coils. The remaining coil portion
> is
> still able to spin the dyno at a much slower than normal speed, and the
> increased current is heating it up fast. I isolated both HV and LV rotor
> windings, they're OK. No other shorts to ground found anywhere in the
> unit.
>
> I'm scratching my head, because the field coils are fed from the primary
> 28
> VDC, so the insulation is not breaking down from high voltage. If there
> was
> a manufacturing fault in the field coil installation, the short would have
> existed from the get-go. How does a fixed field coil insulation break down
> in a few hours of operation? Nothing is grinding, nothing is loose inside
> the dynamotor. It spins completely freely as it should (by the way, there
> is
> a label inside the end bells which says: "Do not lubricate!").
>
> Should I venture and attempt to take the whole dynamotor apart and remove
> the field coils to see if I can find the short?
>
>
>
> Incidentally, my other dynamotor, the older DY-17/ART-13, after replacing
> the HV brush caps (the newer Eicor has no brush caps in the dynamotor
> itself) is working fine. It looks beat-up on the outside, and the
> dynamotor
> itself looks like it was used a lot, but at least so far, so good.
>
>
>
> Any thoughts?
>
>
>
> 73, Meir WF2U
>
> Landrum, SC
>
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