Protecting Against Electrical Discharge Damage

Why AEGIS grounding rings are a proven choice to remediate stray shaft currents


If you’ve ever noticed pits and grooves on your damaged bearings, it was likely caused by electrical discharge. Commonly found in motors driven by Variable Frequency Drives (VFD’s), the pulses that operate these motors often result in unbalanced voltages that can accumulate in the motor shaft and make its way to the ground. These discharges happen so often it can often only take a matter of months before the entire bearing race surface becomes damaged with countless pits known as frosting. Fluting may occur as well, producing washboard-like ridges across the frosted bearing race. Fluting causes audible noise and vibration and is an indication of a catastrophic failure mode.

Regardless of the type of rolling element or raceway damage that occurs, the resulting motor failure often costs thousands of dollars in downtime and equipment failure-related repair or replacement costs.

Preventing Electrical Discharge Damage

The number one solution to electrical bearing damage is to replace standard bearings with ceramic hybrid or insulated bearings. These offer greater electrical and temperature insulation properties, which prevents current discharge and makes them ideal for situations involving VFDs or other grounded motors. The ceramic material provides insulation and non-conductive properties and can operate at low temperatures even under otherwise extreme operating conditions.

Aside from hybrid bearings, it is recommended by Electrostatic Technologies that an AEGIS grounding ring will protect your motor under 100 HP. Above that, it is recommended to use a hybrid or insulated bearing in conjunction with your AEGIS shaft grounding ring, diverting harmful shaft voltages to ground. Voltage travels from the shaft, through conductive microfibers in the ring, through the housing, and finally through the hardware used to attach the ring to the motor to ground.

The shaft grounding ring technology works through a combination of features:

  1. The AEGIS® Shaft Grounding Ring’s unique design features hundreds of
    AEGIS Shaft Grounding Ring to Prevent Electrical Discharge Damage

    AEGIS Ukit Design

    thousands to millions of specially engineered conductive microfibers that encircle the motor shaft. With so many electrical transfer points the ring provides continuous electrical contact, whether its fibers are physically touching the shaft or not. This patented “nanogap” technology enables both contact and noncontact shaft grounding — 100% of the time.

  2. AEGIS® conductive microfibers are a wear-to-fit design that ensures that the fibers don’t “wear out” during the bearing’s life They exhibit minimal wear with the ability to flex without breaking. During the life of the ring, the minimal wear characteristics ensure that the fibers only wear to the exact diameter of the motor’s shaft and no further, maintaining the nanogap contact which allows the AEGIS® Shaft Grounding Rings to continue to operate effectively and protect the motor’s bearings. In testing, they were proven to withstand 2 million direction reversals (to 1800 RPM) with no fiber fatigue or breakage.

AEGIS® Cost Savings Tool


Without proper bearing protection, you may be looking at catastrophic failures and invaluable downtime as you try to assess and repair potential failures. Guarding against electrical discharge damage with grounding ring technology is one of the easiest ways to ensure your bearing will last as long as it was designed to. If you’re interested in finding your AEGIS ground ring or Ukit solution, contact your Bartlett Bearing representative today. A highly-knowledgeable member of our staff will be able to help you choose the right size and specification for your application and is available 24/7/365 to assist with your needs.

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