You accepted a transfer (with a raise!) to be the plant engineer at another production facility. In going over the records, you notice that this plant replaces an awful lot of VFDs and motors. You talk to a few people about it, and they seem to think this is normal. However, you know it's not. In fact, not a single VFD failed the whole time you worked at the other plant. Obviously, fixing this will be good for the plant as well as your career.

What are some steps you should take to stop these unnecessary and costly failures?

While the failure source appears to be a root cause, it may be a specific cause repeated on each installation. Evaluate each VFD/motor installation for:

  • Correct matching of motor/VFD to each other and to the application.
  • Thermal profile (is VFD-controlled motor turning fast enough to cool itself?).
  • Bonding per Art. 250, Part V.
  • Lubrication history (of motor and driven load).
  • Local power factor correction (typically incompatible with VFDs).
Next, look at root causes (e.g., power quality). Hot tip: Ensure your surge protection follows recommended practices; for example, you need a tiered arrangement of SPDs that progressively step down surge voltage.