Rockwell Automation 7000A PowerFlex Medium Voltage Drive (A-Frame) - Classic Control - Manual (Page 207)

Commissioning 4-33
7000 “A” Frame 7000A-UM150F-EN-P – June 2013
Snubber Capacitance (SGCT Device)
Using a capacitance meter, proceed to verify the snubber capacitor
by measuring from the test point to the heatsink adjacent to the right.
Measure capacitance
between heatsink
and test point.
Snubber test point
Figure 4.6 – Snubber Capacitor Test
Refer to Table 4.A to determine the appropriate snubber capacitance
value for the current rating of the SGCT used.
The capacitance measured is actually affected by the snubber
capacitor and other capacitance in the circuit, including capacitance
from the Gate Driver circuit. You are actually looking for a
consistent reading for all devices.
If the capacitor is found to be out of tolerance, refer to Chapter 6 –
Component Definition and Maintenance for detailed instructions on
how to replace the snubber capacitor.
SCR Testing
The following steps outline how to verify SCR semiconductors and
all associated snubber components. A quick reference to the
expected resistance and capacitance values as well as a simple
schematic diagram is located in below: