Rockwell Automation 7000 PowerFlex Medium Voltage (B Frame) Commissioning - ForGe (PanelView 550) - Manual (Page 64)

60 Rockwell Automation Publication 7000-IN006B-EN-P - May 2013
Chapter 5 Commissioning the Drive
Snubber Capacitance (SGCT Device)
Turn the multimeter from the resistance to capacitance measurement mode.
Proceed to verify the snubber capacitor by measuring from the test point to the
heatsink adjacent to the right.
Figure 35 - Subber capacitor test
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 the PowerFlex 7000 ‘B’
Frame User Manual’s “Component Definition and Maintenance” section 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. For quick reference to the expected resistance and
capacitance values, refer to the following table.
Figure 36 shows the snubber
component connections across an SGCT.
Measure capacitance
between heatsink
and test point.
Snubber test point
SCR Rating Sharing Resistance Snubber Resistance Snubber Capacitance
350, 400, 815 Amp 80 Ω 60 Ω 0.5 μf