EMA regularly performs field service on medium voltage vfd s, including the AB (Rockwell) Powerflex 7000 VFD. The following is a brief synopsis of a recent field service call. This particular VFD was located in a waste water facility in upstate New York.
(NOTE: IF you need service on Powerflex 7000 (or any other drive), hit the contact icon on the top right of this page or, click the “Live Support” button if during normal hours)
In this case, the medium voltage VFD faulted when powered up on “Line Cap Fault”. Under normal circumstances, this would indicate bad input filter caps. However, the caps checked fine. Further troubleshooting revealed the input line contractor was not pulling in. This is what normally supplies power to the input filter caps.
We performed a system test, which checks the functionality of the different parts of the Powerflex 7000 VFD individually. The contactor tested fine, but the 56V power supply only had 50V on it. We adjusted the power supply to correct, but that didn’t alleviate the trip. Further troubleshooting revealed that we needed to clear the fault log and save the settings in the NVRAM. (We had this same experience recently during a field service call on a Reliance Flexpak 3000 VFD in Georgia.) Once we cleared the fault log and saved the settings in the NVRAM of the Powerflex 7000, it powered up fine with no “line cap fault”.
We initiated a run command, but received a message on the panel saying the VFD was “not ready.” Even though there were no faults on the Poweerflex7000 at this time, the medium voltage VFD still indicated as “not ready.”
We checked feedback parameters including parameter 324 which displays the line voltage of the VFD. We noticed that the MV VFD indicates 2434V as the line voltage. We knew from the GE Multilin in the cabinet, that the actual input voltage was 4180V. It was apparent that the Powerflex7000 MV VFD was not reading the voltage feedback correctly. We swapped the VSBL (Voltage Sensing Board Line Side) and the VSBM (Voltage Sensing Board Motor side) boards to no avail. The VSB boards feeds into the SCBL (Signal Conditioning board Line Side), so we replaced the input SCBL board on the line side and that resolved the wrong line voltage feedback issue. The Powerflex 7000 now showed the “Ready Status”. We were able to run the MV VFD at this point and got the customer’s equipment up and running.
EMA has a proven record in repairing medium voltage VFDs. Brands include the Robicon Perfect Harmony MV VFD, the WEG Medium Voltage VFD, and the Toshiba T300MVi Medium Voltage VFD in addition to the Powerflex 7000.
Contact your nearest EMA office at the numbers on the bottom of this page, or click “Live Support” on the right if during normal hours.