Rockwell Automation 23P PowerFlex Digital DC Drive - Manual (Page 313)

Rockwell Automation Publication 20P-UM001K-EN-P - July 2014 313
Application Notes Appendix C
Open SCR Test
Under normal drive operation, the load carried by each SCR is relatively equal, as
shown in this image.
If one or more SCRs fail to turn to on, a unique pattern of insufficient or missing
current pulses results, as shown in this image.
Open SCR diagnostics detects SCRs that are not conducting by analyzing the
level of current produced by each SCR pair firing. If an SCR(s) consistently fails
to produce current at a level approximately equal to other SCRs that fired, the
drive concludes that an open SCR has occurred.