Blown rotating rectifier

[adyeeri]

Dear Members,

Pls guide me on our current problem.
We have a 3889 KVA, DIG 161 L/2, 1000 RPM, 50Hz Synchronous generator with Main Exciter 35V, 2.6A and Auxiliary exciter 80V. The unit decoupled from the grid after an over voltage fault on the system, after re-starting, before re-synchronism smoke was observed at the flywheel (N-drive) end, we discovered that the rotating rectifier has blown (Melted) diodes. How can we identify the leads from the Exciter armature and those that go to the rotor field (Attached is the rectifier picture(s)). what insulation resistance readings should we expect on testing. (We can't find the a manual).
Thanks
Adyeeri

 

[waross]

DO NOT CHECK THE RESISTANCES WITH THE RECTIFIER IN THE CIRCUIT.
The lower 4 leads to the copper straps across the rectifiers are DC.
The upper 6 leads are AC.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[adyeeri]

Thanks Bill