Motor bearing failure is the most frequent issue caused by VFDs. But there’s a lot of misinformation out there about what constitutes a VFD-rated motor, so look for “premium VFD insulation” as set in NEMA MG1 Part 31 when purchasing new motors. VFD-rated motors with premium VFD insulation ( specified as NEMA MG1, Part 31) can withstand frequency peaks. That’s why any motor run by a drive should be VFD-rated, AKA inverter duty. This process creates peak voltages high enough to break through motor insulation and short out windings.
VFDs control motors with a simulated AC sine wave known as pulse width modulation (PWM). This problem is caused by extreme peak voltages. Unless you’ve got replacement motors, get ready for lengthy downtimes. And it’s generally going to take more than a couple weeks to do. (1) VFDs Damage Motor Windingsĭamaged motor windings are the most expensive issues VFDs often cause. Copper isn’t cheap and neither is craftsman labor, so a rewinding job can cost you more than half the sticker price of a new motor. This information will be useful if you want to make sure you are getting the best equipment for your needs. Here are five data-backed ways VFDs damage motors as well as some likely solutions. Load-side issues tend to be more difficult to cover with “catch-all” solutions like filters. To help meet these requirements, qualified systems integrators can add harmonic mitigation systems like passive harmonic filters, higher-pulse VFDs and active harmonic filters.Įven if you have a well-written specification that manages VFD created harmonics, you may not have the proper protections in place for the load-side issues VFDs can create. Utility companies manage harmonics through a standard known as IEEE-519. Unless you want the utility company at your door, you’re going to need a plan to solve these issues. In addition, VFDs create harmonics that pollute the power supply. In some cases, motor manufacturers void warranties due to VFD-related failures. For example, some types of bearing failures are attributed to VFD operation, and motor manufactures won’t cover the repair costs in the event of a failure. However, improperly configured drives cause immediate and long-term problems that include very large motor repair bills. They also save money and conserve energy. VFDs are used to start and control the operating speed of electric motors.
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