Siemens/Robicon Perfect Harmony Power Cells (power modules) can be tested in the field, at the job site. Field 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 at our Norcross, GA facility, using a complete Siemens/Robicon Perfect Harmony drive test stand.
It is not always practical to ship Siemens/Robicon power cells (power modules) to a repair facility. EMA can form or reform the electrolytic bus capacitors and put the power cell through a full functionality test, at your facility.
It is not uncommon for customers with critical MV VFDs to be without spare power cells. EMA stocks Siemens/ Robicon Perfect Harmony, Eaton, and Toshiba T300 MVI and MV2 power cells for situations like this. When a customer does have spare power cells, they often sit on the shelf for years before being needed. The issue with this 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 storage without power 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 but it had been stored, without power for over 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. EMA was able to test the cell and reform the capacitors on site, greatly reducing the customer’s downtime.
EMA has been repairing power cells from all generations of Siemens / Robicon Perfect Harmony MV VFDs for the last eight years. The repaired power cells are fully tested for functionality and loaded through our in-house test stand. In addition, we developed the aforementioned capability of testing and reforming individual power cells on site.
Most customers are not aware that a 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 one only needs 480V, 690V or 750V AC depending on the generation of cells. This can all be generated from the 120V wall power or with 480V directly from the low voltage controls of the VFD.
Most of these issues (and several others) can be resolved with predictive and preventative maintenance. Part of our standard procedures during predictive and preventative maintenance to exercise the spare power cells/power modules. EMA offers annual predictive and preventive maintenance on all MV VFDs as well as bus capacitor refurbishment on older MV VFDs with electrolytic capacitors.
If you want to talk with us about any of this, just call 770-448-4644 OR use any of the contact methods on our site, including live chat.
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