Several Variable Frequency Drives (VFDs) were sent into Deltas’ shop for repair. The clients’ complaint for them was that they were failing with an “Overtemp” fault. This is a very common fault/failure on all brands of VFDs. With only a very few exceptions, all VFDs have cooling fans, usually multiple cooling fans. All cooling fans have a finite life span. This lifespan is measured in run-time hours. It is typically several thousand hours, which usually translates into 3-5 years of 24/7 operation. Of course this rating is in a clean environment. The VFD depends upon air flow created by the cooling fans moving air across its’ heat sink fins to dissipate the heat generated by the high power components. The fans and the heat sinks on these VFDs sent if for repair, were completely blocked. Zero air flow was passing through these units. Consequently, they failed on “Over temperature”. Fortunately, the circuitry that detected the over temperature condition, protected the VFD from further damage.
These units, as the photos illustrate, show just how badly the units were blocked. These units required above what Delta typically refers to as a “Level 2” bench cleaning/P.M. service. These may have been a “Level 4” if such a level existed! They had to be completely disassembled, vacuumed, brushed, washed and scrubbed to get all of the foreign matter removed. Then they had to be reassembled and tested. This was to say the least, a very labor intensive process. That translates into a higher than normal cost for the client as well. Since these were large, high horsepower units, it was cost effective to perform the service. In this case, a more frequent preventive maintenance service would have prevented the complete shutdown of these units and would have not incurred the added cost of a bench level cleaning. Delta provides preventive maintenance (P.M.) plans tailored to the specific needs of our clients. Contact Delta at 804-236-2800.