People operating the Siemens Robicon Perfect Harmony medium voltage VFD often don’t realize the need for replacing the bus capacitors after 7 years of operation.
The chance of a bus capacitor failure increases exponentially after 7 years of operation due to degradation of the electrolyte and dielectric material. The situation is exacerbated by increased heat. If the bus caps fail, it can result in damage to the input rectifier section of the cell and the IGBTs, resulting in the line fuses opening, along with other upstream protective devices. The repair cost can be quite expensive on a failed cell due to bad bus capacitors, not to mention that there can be long lead times on the parts.
In fact, this is exactly what happened to a mining company in Nevada recently on their 2000 HP Robicon Perfect Harmony drive. They lost 3 power cells due to capacitor failure. The lead time on the power cells was 16 weeks which forced them to buy a new VFD rather than repair the damaged drive.
EMA now stocks Robicon Power cells for most of the Perfect Harmony Generations up to 1750 HP. We have the capacity to be build one for a 2000 HP if needed. Read about it HERE.
The analogy we use to describe bus capacitor failures in a medium voltage VFD is a timing belt in your automobile. If you do not replace the timing belt at the recommended interval, and it fails while the car is at speed, the damages and repair cost can be catastrophic. In fact, sometimes completely beyond repair.
Its a good analogy for replacing the bus capacitors in the Robicon Perfect Harmony drive. If you let the capacitors run past their time, you might get lucky.. but there’s a real risk of significant damage and downtime. (Luck is not a good maintenance strategy)
We also have a popular blog about bus capacitors.
We would love an opportunity to help you with the needs of all your Siemens/ Robicon Perfect harmony generations. We regularly perform preventive maintenance, including bus cap examination. Hit the contact icon on the right of this page, or call 800-848-2504.
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