Airborne Electrical Generator Question

[u/NoTrainingNoProblem]

I overhaul/test airborne electrical generators (3 phase, 400Hz) and our technical data is very limited. There are differences between various generator models that I'm sure have engineering explanations but our onsite EE was unable to explain them satisfactorily. I'll try reddit instead.

1) All the generators use 6 diode bridge rectifiers on the exciter rotor. 3 diodes are connected to 3 exciter rotor leads which share a busbar with 1 main rotor lead, this setup is mirrored with opposite polarity diodes on the other 3 exciter leads.

One generator uses a capacitor which is inline with the diode busbars while another model uses a resistor on each busbar. Other models use neither and simply have the diode/busbar/main rotor lead configuration.

What is the purpose of the capacitor or resistors in this style of generator? Furthermore what are some fault conditions that would lead to blown capacitors but perfectly intact exciter rotors?

I'll save additional questions for a later post.

[u/Ok-Camera2895]

When you say "in line", do you mean in series? A capacitor in series with rotating diodes trying to pass dc current going to the main field. Would that even work? Resistors in series with rotating diodes would limit current to main fields.

[u/NoTrainingNoProblem → u/Ok-Camera2895]

By inline I mean the capacitor has two leads, one lead is connected to a busbar which has 3 diodes connected to 3 exciter leads and 1 main rotor lead. The other capacitor lead is connected to the other busbar with the reverse polarity diodes. 

Series, parallel I couldn't tell you, I just work on the stupid things.

I'm trying to find out the function of the capacitor to aid in troubleshooting during testing, I don't need a PhD dissertation.

[u/Ok-Camera2895 → u/NoTrainingNoProblem]

The capacitors I have seen on generators in the excitation circuits are to reduce radio static. Although these 400hz military units the function may be different.