Preventing bearing fluting in VFD drives

Used increasingly to save energy, variable frequency drives cause unwanted voltages on motor shafts. If not diverted, the resulting currents discharge through bearings, causing fusion craters on bearing race walls. Over time, this bearing fluting can lead to noise, vibration, failure and catastrophic motor failure.

The Aegis SGR bearint protection ring protects the bearings of VFD-driven motors from electrical damage, and the new universal mounting kit simplifies its mounting on any AC motor shaft.  Available from Electro Static Technology, the kit includes theAegis gounding ring and mounting hardware for most motor designs.  Ordered based on the NEMA “u” shaft diameter, the kit contains the correct size ring for the motor and four styles of brackets with bolts and lock washers that can be used in various configurations, depending on the contours of the motor’s end bracket.

Ideal for motor repair shops, plant maintenance departments, and original equipment manufacturers, the ring prevents electrical “fluting” damage in the bearing, bearing noise, costly motor repairs/replacements, and downtime by safely channeling VFD-induced bearing currents to ground.  To simplify the installation of the ring on NEMA frame motors, the brackets in the U-Kit may be mounted on the motor either by drilling and tapping small holes or using conductive epoxy.   

The ring’s conductive microfibers are embedded securely in a channel and completely surround the motor shaft, providing millions of discharge points for harmful shaft currents. This unique design creates the path of least resistance that effectively diverts these currents away from bearings to ground. The microfibers themselves are specially engineered for exceptional flexibility to prevent breakage. Unlike conventional shaft grounding brushes, the ring is maintenance-free and lasts for the life of the motor.