Preventive Maintenance(PM) on any VFD is in essence downtime prevention. That’s especially true for PM on Robicon Siemens Perfect Harmony VFDs. The Robicon Siemens Perfect Harmony VFD has been around a long time. Siemens Robicon did a great job at providing a reliable voltage 
source medium voltage VFD at a time when few others could. The Siemens Robicon Perfect Harmony VFD is found in applications world wide, and many of them have been operating for over 10 years. Preventive Maintenance (PM) on the Siemens Robicon Perfect Harmony VFD is a great investment.
This image is a Robicon Siemens Perfect Harmony drive that suffered a catastrophic failure. We were asked to evaluate and eventually replace this unit. 
Over the years we’ve seen a number of failures (not all as bad as this one) due to a lack of routine preventive maintenance (PM). The Robicon Siemens Perfect Harmony VFD uses electrolytic capacitors in the DC bus. Over time, these capactitors begin to age. (See our blog Robicon Perfect Harmony Capacitor Failures)
Preventive Maintenance (PM) on Robicon Siemens Perfect Harmony VFDs can spot and alleviate a number of issues, including electrolytic caps that are on the verge of failure.
Per the IEEE, failure rates are 3 times higher on systems not subjected to regular PM. Robicon Siemens Perfect Harmony VFDs (and for that matter ALL medium voltage VFDs) cost a great deal of money, AND are hard to replace due to their physical size. Therefore a PM (Preventive Maintenance) program on Robicon Siemens Perfect Harmony VFDs makes economic sense.
What causes failures? Moisture and loose connections are responsible for almost one half of failures. Those failures in a Robicon Siemens Perfect Harmony VFD can be very expensive, and in some cases even disastrous.
PM (Preventive Maintenance) on Robicon Siemens Perfect Harmony VFDs usually involves the following:
- Visual, thermographic, or other non-invasive inspections prior to shutdown
- All circuit breakers/disconnects repeatedly opened and closed to insure proper operation
- Protective Relays and Devices tested and calibrated
- Test oil samples from all oil filled equipment (transformers)
- Electronic equipment inspected, cleaned, and tuned
A major preventive and predictive maintenance consideration for Robicon Siemens Perfect Harmony VFDs is the aforementioned bus capacitors.
Per most manufacturers, the expected life span of bus capacitors is 7 years. This time can be affected by voltage levels and temperature. Higher voltages shorten the life, as do higher temps.
Another overlooked item in preventive and predictive maintenance (PM) on Siemens Robicon Perfect Harmony VFDs is cooling fans. It is an easy item, along with filters, to overlook. Higher temps will shorten the life of a number of drive components.
So, if you’re running Siemens Robicon Perfect Harmony VFDs.. give predictive and preventive maintenance (PM) some thought. You can reach us at 770-448-4644.. or via the online contact methods on this site (Including Live Web Support on the right of this page) . We have complete Robicon Perfect Harmony test stands for the cells, we have spare parts, and provide field service world wide on Siemens Robicon Perfect Harmony VFDs. No One, Anywhere is Better at Drives than we are. Talk to us!
2 Responses
I heard that perfect harmony VFD power cells cannot be stored for long periods of time before needing reformation. we are developing a reformation plan and would like to know how often should we reform the power cells. I’ve heard 6 months and I’ve heard 1 year. which is it, thanks.
We typically suggest once a year. Since preventative maintenance should be done once a year, that is a good time to rotate your spare cells into the drive, thus keeping them always reformed.