Rockwell Automation MV SMC Flex Motor Controller (for Series K or later) - Manual (Page 133)

Rockwell Automation Publication 1560E-UM051F-EN-P - June 2013 123
Troubleshooting Chapter 9
Power Circuit
Troubleshooting Thyristor (SCR) Testing
If a power semiconductor is suspected of malfunctioning, it may be checked as
follows:
1. Remove all power from the equipment.
2. Measure DC resistance per the following chart:
Table 24 - SCR Resistance Measurements
3. If a short circuit is suspected, the SCR must be isolated from all
surrounding circuitry (i.e. unplug gate and cathode leads, and remove
snubber and resistor circuit leads from the driver boards). Measure
resistance to confirm state of the SCRs. If the SCRs are not shorted,
proceed to snubber and resistor circuit testing, following this procedure.
4. If a faulty device is found, the entire heatsink assembly must be removed.
5. Complete heatsink assemblies with matched SCRs are available as a
renewal part (see
Appendix G ). In most cases, the assembly can be
dismantled to replace the SCRs.
SHOCK HAZARD: To avoid shock hazard, ensure the main power has
been disconnected before working on the controller, motor or control
devices. Verify that all circuits are voltage free using a hot stick or
appropriate voltage measuring device. Failure to do so may result in
burns, injury or death.
Location of Probes 1000V 1300V 1500V 2300V 3300V 4160V 5500V 6900V
Cathode to Cathode (KOhms)
(1)
(1) Measured between terminals “Cathode” on CLGO Boards, upper two or between two within a phase.
- - - - 22-30 23-31 21-29 24-32
Cathode to Cathode (KOhms)
(2)
(2) Measured between terminals “Cathode” on CLGO Boards, top to bottom within a phase.
17-23 19-25 20-27 21-29 40-53 43-57 60-90
(3)
(3) Measured between line and load terminals within a phase.
64-84
(3)
Cathode to Gate (Ohms) 10-40 10-40 10-40 10-40 10-40 10-40 10-40 10-40
TIP The actual resistance value depends on the ohmmeter used, the
particular brand/rating of SCR and external circuit influences. It is
impossible to accurately measure the condition of the SCR when it is
unclamped!
ATTENTION: For heatsink assemblies containing four or more SCRs, the
entire matched set shall be replaced. Devices connected in series must
have performance specifications matched for proper operation. Failure
to use matched sets may result in damage to the devices.