Rockwell Automation 7000A PowerFlex Medium Voltage Drive (A-Frame) - Classic Control - Manual (Page 338)

6-34 Component Definition and Maintenance
7000A-UM150F-EN-P –June 2013 7000 “A” Frame
Snubber Resistors
Snubber resistors are connected in series with the snubber capacitors.
Together they form a simple RC snubber that is connected across each
thyristor (SCR or SGCT). The purpose of the snubber circuit is to reduce
the dv/dt stress on the thyristors and to reduce the switching losses. The
snubber resistors are connected as sets of various wire-wound resistors
connected in parallel. The number of resistors in parallel depends on the
type of the thyristor and the configuration and frame size of the drive.
Testing Snubber Resistors
Access to the snubber resistor is not required to test the resistance.
Located within the PowerCage under the heatsink is a snubber circuit test
point. For each device, there is one test point. To verify the resistance,
follow the procedures outlined in Chapter 4 – Commissioning.
Measure resistance between
heatsink and test point.
Snubber resistor test point
Figure 6.25 – Testing the Snubber Resistor