All electric motors controlled by variable frequency drives are at risk of electrical bearing damage. Motors in hazardous locations have the added problem that protective measures, like shaft grounding, are restricted. But for the past 10 years or so, this has been changing.
In Class I Divisions 1/2, and Zones 1/2, potentially explosive gases may be present. The risk of ignition must be kept as low as possible. Shaft grounding devices are considered sparking devices, and so are tightly restricted.
Much of what follows focuses on motor manufacturers, because they are better able to navigate the process of testing motors with shaft grounding for compliance. Buying motors for hazardous locations with AEGIS® Shaft Grounding Rings already installed is the easiest way for users to ensure their motors have electrical bearing protection.
Shaft Grounding in Class I Division 1/Zone 1 Areas
In Class I Division 1 and Zone 1 locations, combustible gases are often present during normal operation. Because of the high risk of ignition, explosion proof (XP) or Ex d motors must be used in these areas. As early as 2014, procedures were developed for installing AEGIS rings inside XP or Ex d motors, outside of the flame path.
Marathon Blue Chip® Hazardous Duty® motors with part number suffix -P include AEGIS bearing current protection standard. Other brands offer AEGIS as an option, including WEG Electric’s WX22db and Explosion Proof motors.
Shaft Grounding in Class I Division 2/Zone 2 Areas
In Class I Division 2/Zone 2, explosive gases are not typically present. IEEE-841 Standard motors are often used in these locations. Shaft grounding can be used in these areas, if it is shown to be safe by a set of non-incendivity calculations. But who should perform this verification?
The formulas involved use properties of the motor and its components that a motor user would have a hard time finding. It would typically be easier for the motor manufacturer to verify non-incendivity than for a user.
As of October 2025, WEG and Wolong have gone through this process. WEG’s W22 Cast Iron motors can have AEGIS rings factory-installed and be CSA-certified for use in Class I Div. 2 areas. Wolong’s GE Industrial Motors low voltage ULTRA and QUANTUM lines can be CSA-certified Ex ec with AEGIS for use in Zone 2.
Summary
- The best way to use shaft grounding in classified areas is to buy a suitable motor with AEGIS Shaft Grounding Rings factory-installed
For Class I Division 1 and Zone 1 areas:
- Marathon Blue Chip Hazardous Duty motors with part numbers ending -P include AEGIS standard
- AEGIS can be factory-installed as a mod in other Marathon XP motors, and in WEG XP and Ex d motors
For Class I Division 2 and Zone 2 locations:
- WEG W22 Cast Iron motors can be certified for these areas with AEGIS installed
- Wolong’s low voltage GE ULTRA and QUANTUM with AEGIS can be certified Ex ec
AEGIS Rings come with a 2-year extended warranty against bearing fluting damage. No other form of protection against VFD-caused bearing damage offers a warranty like this.
To learn more about AEGIS shaft grounding and best practices for electrical bearing protection, sign up for a training. We offer monthly live training webinars, and we can also visit your facility to review your exact application.
