Marathon Electric offers the industry-leading line of Hazardous Duty™ Division 1 Explosion Proof, NEMA Premium® XRI®, Class I and II, Groups C, D, F & G motors. Marathon’s unique design, combined with AEGIS® Shaft Grounding Ring technology and Marathon’s work with Underwriters Laboratory (UL), minimizes the risk of bearing damage. Marathon’s “BCP” System, featuring the AEGIS Ring, meets all UL requirements while protecting the motor bearings.
With the growing emphasis on energy savings, process engineers, as well as plant maintenance personnel, have turned to variable frequency drives (VFDs) to improve process reliability, uptime, and safety (particularly in hazardous locations) for critical applications. Using VFDs also reduces the energy consumption of the electric motors in their facilities.
It is well documented that the common mode voltage of VFD output can contribute to bearing failures in drive/motor systems. Unfortunately, unexpected bearing failure can offset much of the savings initially anticipated by the use of VFDs. Effective shaft grounding helps prevent the destructive effects of common mode voltage in these critical applications, facilitating maximum energy savings and reliability.
The option of the AEGIS shaft grounding rings factory installed in these motors is available across the entire product line and comes in stock through 50 HP. The Marathon XRI Explosion Proof Severe Duty motor with “BCP” provides maximum energy savings potential when used with VFD’s, enhanced reliability and uptime, and the “peace of mind” end users demand from their motor/drive systems. Marathon is the only supplier of Division 1, Class I and II Explosion Proof motors with factory-installed AEGIS long-term bearing current protection from VFD-sourced damage!
The Marathon XRI Severe Duty Explosion Proof motor is UL Listed and CSA Certified for use in virtually any hazardous process application. The product features cast iron construction, epoxy interior and exterior paint, Max Guard insulation system, precision balance, thermostats and a generous 3-year warranty.
For more applications information on how you can protect your motors from electrical bearing damage download the AEGIS Best Practices Handbook.
Underwriters Laboratories (UL) has an approved set of procedures for installing AEGIS® shaft grounding rings inside explosion proof (XP) motors. XP motors with AEGIS® rings installed according to these procedures may be used in hazardous environments, Class I: Division 1.
The following diagrams are the approved installation locations inside the XP motor.
Note: In Class I: Division 2 designs. Because shaft grounding devices must be installed inside explosion proof enclosures (as per IEEE 303) for Class I: Division 2, they may not be installed internally or externally in/on a non-XP motor.
At this time, Marathon Electric is the only electric motor manufacturer marketing XP motors with AEGIS® shaft grounding protection installed inside. They range from 3 HP (182T Frame) to 50 HP (326T Frame) and Marathon Electric will install AEGIS Rings in larger models. For more information on Marathon Hazardous Duty motors with AEGIS® Inside. For catalog numbers and pricing, see the highlighted “-P” motors on the Hazardous Duty™ pages of the 2014 catalog.
To install AEGIS® rings in explosion proof motors in a hazardous environment, a motor repair shop must first be UL approved to work on all XP motors. They must then apply for certification for the addition of adding shaft grounding to their UL binder and then demonstrate adherence to the additional set of procedures required for installing shaft grounding inside of XP motors.
Motor repair shops with UL certification to work on XP motors and certification of their ability to add shaft grounding can “rework” any size explosion proof motor and then re-nameplate the motor as explosion proof. The drawing below was created by UL to show where the ring must be installed to comply.