Stumped by welder exciter generator
Stumped by welder exciter generator
(OP)
A friend had me look at his old Lincoln gas powered welder that his repair guy can't fix. It has a two pole 120V DC exciter on the end. It went bad when a worker pluggrd in a transformer type battery charger to the 120V DC convenience outlet.
When I first saw it the armature was pulled out. Dusty but no signs of windings burning, overheating or commutator arcing. Tapped a screwdriver to the field coils and almost no sign of residual magnetism. The 145 ohm field coil was isolated and connected to 12V. That gave me 5V at the brushes with the engine running. Reversing the field polarity gave me -5V at the brushes. Seemed simple enough, just needed to flash the coils.
Next day connected 140V DC to the field to flash it. With the field reconnected and a 100W lamp connected as a load I started the engine. Output was only a little over a volt. Then I powered the field independently with 80V DC. That gave it a really strong magnetic field. Still only a couple volts output. The commutator has been cleaned. Armature has continuity all around. Brushes make good contact. Resistance from brush to brush is around 1.5 ohms. There is just no sign that anything is wrong. Field does have an additional low ohm winding which I assume is to boost voltage to compensate for IR loss. It was not connected durring testing. Welder section works normally when independently powered with 100V DC. I can't imagine an armature failure mode that would cause this. Appreciate any ideas.
When I first saw it the armature was pulled out. Dusty but no signs of windings burning, overheating or commutator arcing. Tapped a screwdriver to the field coils and almost no sign of residual magnetism. The 145 ohm field coil was isolated and connected to 12V. That gave me 5V at the brushes with the engine running. Reversing the field polarity gave me -5V at the brushes. Seemed simple enough, just needed to flash the coils.
Next day connected 140V DC to the field to flash it. With the field reconnected and a 100W lamp connected as a load I started the engine. Output was only a little over a volt. Then I powered the field independently with 80V DC. That gave it a really strong magnetic field. Still only a couple volts output. The commutator has been cleaned. Armature has continuity all around. Brushes make good contact. Resistance from brush to brush is around 1.5 ohms. There is just no sign that anything is wrong. Field does have an additional low ohm winding which I assume is to boost voltage to compensate for IR loss. It was not connected durring testing. Welder section works normally when independently powered with 100V DC. I can't imagine an armature failure mode that would cause this. Appreciate any ideas.





RE: Stumped by welder exciter generator
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If we learn from our mistakes I'm getting a great education!
RE: Stumped by welder exciter generator
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Stumped by welder exciter generator
rasevskii
RE: Stumped by welder exciter generator
RE: Stumped by welder exciter generator
If the field is bad, this may make it worse and easier to find the failure.
Bill
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"Why not the best?"
Jimmy Carter
RE: Stumped by welder exciter generator
RE: Stumped by welder exciter generator
Bill
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"Why not the best?"
Jimmy Carter
RE: Stumped by welder exciter generator
40 years ago I rewound by hand a generator for slower speed by hand. An experience I never want to repeat. Forget how the coils went. With mltiple paths I still would have expected some output.
RE: Stumped by welder exciter generator
Bill
--------------------
"Why not the best?"
Jimmy Carter