OM2042 7/11 Safety - Section 20
Page 20-21
Failure of the Discharge System
If the capacitor charge lights remain illuminated, a
failure of the normal (fast) capacitor discharge sys-
tem (RP discharge path) has likely occurred. The
slow discharge resistors that are hard wired across
the DC link should then discharge the capacitors.
The slow discharge resistors will discharge the DC
link to less than 1 VDC in under 7.5 minutes. If after
7.5 minutes, the capacitor charge lights are still illu-
minated, it must be assumed that the automatic dis-
charge system is not working and that high voltage is
present in the high voltage area.
1. Open the high voltage area doors.
2. With a suitable high voltage meter rated for at
least 2000 VDC, such as PC3186 or equivalent,
plus suitable protective equipment, measure the
voltage across each of the DC link capacitors.
Place one meter lead on the positive (+) capaci-
tor terminal, and the other meter lead on the
negative (-) capacitor terminal, and observe the
voltage. See Figure 20-7 and Figure 20-8. If the
voltage is less than 1.0 V the capacitor is suffi-
ciently discharged. Repeat on all DC Link
capacitors. If the voltage of any capacitor is
above 1.0 V, manually discharge the capacitor
as described in Manual Discharge of
Capacitors on page 30-22.
FIGURE 20-7. DC METER ON CAPACITOR
FIGURE 20-8. CAPACITOR TERMINAL POLARITY
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