Definition:
The PFN's charging current exceeded 5.7 amps.
Theory:
The "Charging Switch" (A10) provides current to the "charging transformer (T2) in the oil tank from the 280 Volt power supply. The collapsing of the magnetic field in T2 induces a charge on the PFN through the diode assembly (A12A5). Taps off of T2 provide samples which are monitored for over current and voltage conditions by the charging switch. The amount of charge is dependent on the amount time the charging switch develops the magnetic field of T2. The duration of charge is set by A1R3 for long pulse and A1A2R74 for short pulse. A1A2R74 is wired to the wiper of A1R3, adjustment of A1R3 will effect A1A2R74 adjustment.
Sampling Point(s):
The charge current is sampled using taps on T2 in the oil tank. See figure 11-5 sheet #3, upper right.
Detection/Threshold Point(s):
The sample is detected in the charging switch (A10). See figure11-5 sheet 2, lower left.
Supporting Indications:
PFN meter (A1M5) may display a abnormally high value if you are running at a high PFN voltage or low if the PFN and related components are producing a high load (low impendence circuit).
The PFN meter will show no voltage once the alarm is set. The termination of PFN charging will allow the discharge of the PFN. The time required to discharge the PFN is too short for a analog meter to detect. Use of a scope to capture (single sweep, trigger sweep, etc.) the PFN voltage at A12TP1 will allow the technician to observe the PFN voltage. Proper discharge of the PFN can be determined by observation of the PFN wave form.
The E/I meter position #14 displays the PFN charge current.
Conflicting Indications:
None
.
Supporting Documentation:
EHB 6-511
Last Updated on June 17, 1998