Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C Frame) - Classic Control - Manual (Page 385)

Component Definition and Maintenance 6-41
7000 “C” Frame 7000L-UM300I-EN-P – June 2013
Figure 6.32 – Typical Torque Sequence
Snubber Resistors
A test point is provided inside the PowerCage to measure the
resistance of the snubber resistor and capacitance of the snubber
capacitor. The test point is the electrical connection between the
snubber resistor and snubber capacitor. The procedure is to place
one probe of the multi-meter on the test point and the other probe on
the appropriate chill block to determine the value of the resistor or
capacitor.
Snubber resistors are connected in series with the snubber capacitors.
Together they form a simple RC snubber that is connected across each
semiconductor (SCR or SGCT). The purpose of the snubber circuit is
to reduce the dv/dt stress on the semiconductors and to reduce the
switching losses. The snubber resistors are connected as sets of thick
film resistors. The number of resistors depends on the type of the
semiconductor and the configuration and frame size of the drive.