Rockwell Automation SD3000 Drive Configuration, Programming - Manual (Page 88)

Appendix B
Continued
Open SCR Diagnostic Variables
The open SCR diagnostics are used to make certain that all SCRs in the Power Module are, on the average,
carrying the same load. The current flow through each SCR is compared to the average current being
supplied by the Power Module. If an SCR is not carrying its share of the load, that SCR or SCR pair in the
case of a regenerative drive, will be identified in register 204/1204, and a warning will be reported in register
203/1 203. This diagnostic is run by the PMI Processor operating system every time an SCR is fired. SCR
diagnostic failures are usually due to broken wires, faulty SCRs, or faulty gate drivers in the Power Module.
However, the diagnostic routines may need to be adjusted due to unbalanced A-C line voltages or unusual
operating conditions. In this case, the programmer may need to adjust the tunable gain values used in the
diagnostic routines in order to make the system more tolerant of unusual conditions that are found in the
application.
The SCR diagnostic tunable values listed below determine the level of error reporting that will occur. If the
default CURRENT values are not acceptable, the programmer must either change them or tune them on-line.
The STEP parameter for all the variables is always 1 (one).
l SCR_GAN% - SCR Diagnostic Gain
Default Current Value: 100
Low Limit: 1
High Limit: 500
Step: 1
The units are in counts.
l SCR_DECAY% - SCR Diagnostic Decay Rate
Default Current Value: 99
Low Limit:
1
High Limit: 99
Step: 1
The units are in counts.
l SCR_DBAND% - SCR Diagnostic Deadband
Default Current Value: 10
Low Limit: 0
High Limit: 50
Step: 1
The units are in percent.
l SCR TRIP% - SCR Diagnostic Trip Point
Default Current Value: 1500
Low Limit: 1500
High Limit: 3000
Step: 1
The units are in counts.
B-4