Motors controlled by variable frequency drives (VFDs) are often vulnerable to electrical bearing damage caused by shaft voltage discharge. The risk of premature bearing failure can be mitigated by shaft grounding, but this is problematic in hazardous (classified) environments where potentially explosive gases may be present.

Background

Installing motor shaft grounding in hazardous areas has always been challenging due to shaft grounding devices being classified as “sparking” devices. In 2014, Underwriters Laboratory approved procedures for installing shaft grounding rings in explosion-proof (XP) motors for Class I, Division 1 areas. There are similar procedures for Ex/ATEX motors. The shaft grounding device is installed outside the motor flame path in both cases.

It was only in the early ’20s that changes in electrical codes and IEEE standards opened the way to use shaft grounding on (non-XP) motors in Class I, Division 2 areas. The catch is that first, so-called non-incendivity calculations must be performed to determine that the shaft grounding device spark energy will not ignite the gases in the classified area. The measurements required for these calculations are beyond many motor users’ means, and until mid-2024, no motor manufacturers had yet confirmed that their products could be certified for Class I, Division 2.

WEG W22 Motors Can Now Be Certified

In July 2024, WEG Electric Corp. announced that their entire W22 line of cast iron motors has been evaluated by CSA Group to satisfy both the IEEE-1349 discharge energy calculation and IEC 60079-0 standard. That means these motors can be equipped with shaft grounding and used in Class I & Class II Division 2 areas. They can be purchased with AEGIS® Shaft Grounding Rings factory installed and installed without the user needing to do any calculations.

In a word, it just got a whole lot easier to protect motors in hazardous areas from electrical bearing damage. As a bonus, the W22 line also includes IEEE-841 Std motors. 841 motors are some of the most robust and reliable motors there are, and some motor users use 841 motors throughout their facilities just to be sure they’re using the best available. With AEGIS rings installed, these motors will be even more reliable.