Siemens / Robicon Perfect Harmony Power Cells (power modules) can be tested in the field, at the job site. Field or site testing the Perfect Harmony Power Cells (power modules) takes special equipment, which we developed, exclusively for testing the Siemens / Robicon power cells (power modules). We also repair and test the power cells in our Norcross, GA facility, using a complete Siemens / Robicon Perfect Harmony drive test stand.
However, it’s not always practical to ship the Siemens / Robicon power cells (power modules) to a repair facility, particularly if you just want to know IF your spare Siemens Robicon Perfect Harmony power cells are operative. When we field or site test the Siemens / Robicon cells (modules) we can actually form (reform) the electrolytic bus capacitors, and put the cell through a full functionality test.
It is common to find customers with critical MV VFDs without spare power cells or as they are sometimes called, power modules. We stock Siemens / Robicon Perfect Harmony, Eaton, and Toshiba T300 MVI power cells to assist in those instances. When they do have spares, the power cells / modules can sit on the shelf for years before being needed. The issue with that on the Siemens/ Robicon harmony MV VFDs, is the electrolytic capacitors within the cells deteriorate when sitting for more than a year without power applied. Electrolytic capacitor manufacturers and VFD manufacturers recommend that the capacitors or power cells be reformed after sitting on the shelf for more than one year. (See our blog on VFD Capactitor Failures)
Recently, an oil and gas pipeline industry facility had power cells fail on their 4160V 3000 HP GEN3 Harmony VFD (Siemens) . They had a spare power cell that had been sitting for six years. When they called the manufacturer, they were told the power cell could not be reformed and properly tested in the field. The manufacturer recommended that the customer ship the power cell to the factory for proper reforming of the capacitors and testing of the power cell. We were able to test the cell and reform the capacitors on site, greatly reducing downtime.
EMA has been repairing the power cells from all generations of Siemens / Robicon Perfect Harmony MV VFDs at our shop for the last eight years. The repaired power cells are fully tested for functionality and loaded through our in house test stand. In addition to that we developed the aforementioned capability of testing and reforming individual power cells at the customer’s site.
Most customers are not aware that the cascaded H-bridge topology only requires a low voltage source for each power cell. So to reform and test the power cells from the Harmony MV VFDs depending on the generation of the MV VFD, you may need 480V, 690V or 750V AC. This can all be generated from the 120V wall power or with the 480V directly from the low voltage controls of the VFD.
This issue can also be resolved and prevented by doing predictive and preventative maintenance on the MV VFDs. It is part of our normal routine during predictive and preventative maintenance to exercise the spare power cells/power modules. EMA offers annual predictive and preventive maintenance on all MV VFDs and also offers bus capacitor refurbishment on older MV VFDs with electrolytic capacitors.
If you want to talk with us about any of this.. nothing could be easier. Just call 770-448-4644 OR use any of the contact methods on our site, including live chat.
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