Manual Discharge Of Capacitors - Komatsu 930E-4SE Operation & Maintenance Manual

Safety - Section 20
Page 20-22

Manual Discharge of Capacitors

If the voltage is greater than 1V on any of the capaci-
tors, the capacitor must be manually discharged.
With a suitable capacitor discharge device, such as
ground stick pair (PC3299), discharge the capacitors
where needed per the following instructions:
1. With the control cabinet high voltage compart-
ment doors closed, connect the ground stick
pair ground lead to ground. The most conve-
nient location is the middle top bolt that
attaches the door center post to the control cab-
inet frame.
2. Verify the ground connection and ground stick
resistance levels. Measure the resistance
between each individual ground stick tip to
either the GND1 or GND2 ground block in the
low voltage compartment of the control cabinet
using a multimeter (Figure 20-9). Ensure that
the resistance is within the manufacturer's
specifications for the ground sticks.
For PC3299 grounding sticks, the valid range is
80 to 125 ohms per stick.
Hazardous voltages are present in this equip-
ment. Avoid touching any energized equipment
when the door to the low voltage area is open.
Failure to do so may result in personal injury and
equipment damage.
FIGURE 20-9. GROUNDING STICK LEAD CONNECTION AND CHECK
3. Discharge the relevant capacitors. Open the
door(s) and place one grounding stick on one of
the positive (+) capacitor terminals and the
other on the diagonally located negative (-) ter-
minal. Refer to Figure 20-8 and Figure 20-10.
Attempt to minimize the time between applica-
tion of the positive stick and the negative stick
so that the current flow will be positive to nega-
tive rather than either to ground. Leave sticks in
place until capacitors are discharged. Refer to
Figure 20-10.
NOTE: On the capacitors located behind the door
post, it is difficult to access diagonal terminals on the
same capacitor. If using adjacent terminals, use care
to keep the tips separated while discharging or else
use a positive terminal on one capacitor and negative
terminal of the adjacent capacitor on the same bus
bar.
For PC3299 grounding sticks, the discharge times
from 2000 volts are:
• 15 seconds (maximum) for 2 capacitors
• 75 seconds (maximum) for 10 capacitors
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