Hi Group,
Not sure if I have the right group, looking for info on a replacement part
for a Caterpillar 200 KW AVR.
The generators voltage regulator board uses a selenium rectifier as a
snubber for overvoltage protection for the SCR's in the field winding ckt.
The SCR's are fuse protected with 70 amp 600 Volt diode fuses.
These fuses blow when a large load is applied. (when my refridgeration
compressor turns on).
Voltage regulation is stable and the AVR shows no signs of malfuntion
other
than the blowing of the field scr fuses. The engine governer responds
properly and no "droop" occurs during a large load. The fuses seem to blow
only once in a while, this leads me to believe the old seleniums are
begining to fail. The choke and caps in the LC tank ckt test fine. The
large
spike reflected into the field ckt from the stator are not being "snubbed"
properly by the seleniums, or so I suspect.
The rectifiers are arranged back to back across the SCR's in the field
winding ckt. The field ckt is a ****tion of the main stator winding that
feeds the field winding, rectification and conduction is controlled by
SCR's, also in the ckt are an LC arrangement to control transients. The
schematic shows the back to back selenium rectifiers as zeners, so they
have a conduction cutoff voltage.
What would I replace the seleniums with?????
any ideas appreciated. Not sure what the field control voltage is,
suppose
I should get in and make some measurements.
No one manufactures seleniums that i could find, the original part was
manufactured by IR.
any help appreciated,
Capt. Vin Collins
F/V Sun Dragon
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