Burning of Excitation Rotating Diodes

Overcurrent.

...probably caused by short circuit in the field windings. Assuming that this is the same generator from your previous posts then the reason is that you did not perform any of the electrical tests that are mandatory after energizing a generator at zero speed.

Any chance a poltergeist has reversed phase sequence? S.M.

bet this is a PMG excited gen. An AVR usualy does't open the rotating diodes when they fail, i find them still in the shorted failure mode but a PMG will make enough current to blow them open after they fail shorted and i find them burned open

Check the PMG and it's exciter Faiz

1) overcurrent

2) you need to replace higher kva than you ussage full load

3) calculate your full operation load in your facilities then chose the generator fit for!

example : your full load is 100kw you need to have 200kw generator

if you do this this will not give you a exciter doid burn out !!!!