Rockwell Automation 1560E SMC Flex Smart Motor Controller - Manual (Page 145)

Troubleshooting 9-27
If the resistance checks from the Thyristor testing section were abnormal
and the thyristors checked out OK, there may be a problem in the snubber
or resistor circuits.
1. Remove all power from the equipment.
To avoid shock hazard, ensure main power has been
disconnected before working on the controller, motor or
control devices. Verify that all circuits are voltage free
using a hot stick or appropriate voltage measuring
device. Failure to do so may result in burns, injury or
death.
2. Check the snubber components and sharing resistors by isolating them
and measuring values as follows (See Figures 9.21 to 9.26):
RS 60
Ω
(180 and 360A)
30
Ω
(600A)
CS 0.5 or 0.68 µF (180 and 360A)
1.0 µF (600A)
RRx 32.5 k
Ω
total, taps at 2.5 k
Ω
from each end
(x = 1, 2 or 3)
Replace any out-of-spec components. See Renewal Parts listing in
Appendix D.
3. If the snubbers and sharing resistors are within tolerances, check the
resistance of the voltage sensing module (refer to Figure 9.20).
Remove the ribbon connector from J1 by pressing down on the locking
tabs then gently pulling the connector out. Take note of which tap the
white high voltage wires are connected to, then remove them (L1, T1,
L2, T2, L3, T3). Measure the resistance between each tap and the
ground connection, and compare to the values in Figure 9.20.
S H O C K H A Z A R D S H O C K H A Z A R D
Snubber and Resistor Circuit
Testing