Testing generator parts

Posted by Bob Carabbio on April 03, 1998 at 22:26:04

In Reply to: Testing generator parts
posted by Bob East on April 01, 1998 at 07:26:39

The resistances of the coils (particulary the armature) VERY low.
With the ground terminal in place, the field should measure about 1.1 ohms to ground.
Disconnect theground terminal of the field disconnected, there should be an infinite reading to the case.In a lot of cases the reading is more like 100,000 ohms which is still good. any Short or low resistance is fatal for the field coils. much less than 100K ohms indicates that
the insulation is pretty far gone.
The armature should also measure >100,000 ohms between the commutator and the shaft.Any short or low resistance here is fatal.
All the coils look like shorts so a Growler is necessary find actual shorted windings. however-
If the coils are good, the generator should "Motor" smoothly at about around 200-300 rpm drawing a relatively even 5 amps with 6 volts applied. Make sure the bearings are free before motoring the generator.Tight bearings will cause the current to be high.if the current is very high, then there is probably a field priblem.if the motoring is uneven with pulsating rotation and current, there's an armature problem
- possible shorted winding, or uneven commutator (if it hasn't been machined).The generator should draw about 20 amps if it's powered at 6 volts with the shaft locked (don't do this for long).
The Field should draw 5.2 amps if you lift the third brush off the commutator, and apply 6 volts to it with the ground connected to the case.
Bob Carabbio.

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