Manual MRR1 GB
Woodward
DOK-TD-MRR1 Rev.A
11
Diode failure protection:
The diode failure protection is based on the measurement of the ripple component of the excitation
current related to the mean value of the excitation current as per following formula:
%
,
,
· 100
Typical values for Ir:
All diodes all right:
Ir
≈
15...20%
One diode open:
Ir
≈
110%
One diode short:
Ir
≈
200%
The setting of Ir> should be chosen at about 40% to 50%. The tripping time tIr should be instanta-
neous or with only a small delay, e.g. 200 ms. In case of a diode short the rotor system is extreme-
ly endangered!
Hint!
The required settings depend on various factors like:
- Required power factor of the generator
- Required minimum short circuit duration etc.
