Lucent Technologies Lineage
®
2000 400A, 60Hz Ferroresonant Rectifier J85503C-3
7 - 14 Troubleshooting and Adjustments
Issue 10 July 2000
1. Loosen the locking screws and open the front door of the rectifier.
2. Locate the CM3 digital meter board on the inside of the front door.
3. Locate the R15 potentiometer on the meter board (see Figure 7-1).
R15 is easily accessible on the component side of the board. The
CM3 board can be calibrated without removing the board from the
support standoffs.
4. Adjust the load so that the rectifier delivers approximately 200
amperes, 50% of its rated current capacity.
5. Connect a DMM, set on the dc millivolt scale, across test points
E25 and E26 on the 329 Circuit Module. See Figure 6-2.
6. Observe the DMM and record the rectifier’s shunt voltage. The
shunt is rated 500A/50mV = 10A/mV (each millivolt of voltage
drop across the shunt indicates 10A of output current).
7. Convert the DMM voltage reading to amperes. For example, if the
DMM reads 20mV, then 20mV X 10A/mV = 200A of output
current.
8. Compare the amperes calculated in Step 7 with the digital display
of the rectifier meter while the switch is in the AMPS position.
9. Compare the amperes calculated in Step 7 with the rectifier digital
display while the switch is in the AMPS position. If the rectifier
display is not between ±2% ±2A of the amperes calculated in Step
7, calibrate the CM3 card via its R15 potentiometer.
10. If the meter cannot be calibrated, replace the CM3 digital meter
board per Section 8 and repeat this procedure from Step 1.
Table 7-G: Digital Meter Tolerance
Switch Position
Tolerance
Rect V
± 0.1 volt
Amps
± 2.5% of reading ± 2 amperes*
*To compare, measure the shunt voltage. 1mV of shunt voltage
indicates 10 amperes of output current. For example, the shunt
voltage should be 40 mV at full load (400 amperes). At 125% of full
load (500 amperes), the shunt voltage should be 50 mV.
