Electric motors are the backbone of many industrial operations. When they fail, the repercussions are be costly and disruptive. One common culprit behind motor failure is bearing damage caused by stray electric current. Understanding how to protect bearings helps maintain the reliability of your machinery.
Why Bearing Protection Is Essential
Variable Frequency Drives (VFDs) are widely used to control motor speed and reduce energy use. However, they produce a common-mode voltage, which induces a voltage across the motor bearings. This voltage tends to discharge by arcing through the bearings. This leads to electrical pitting, and over time the pits can cause frosting fluting, and eventual bearing failure.
Bearing failure doesn't just mean replacing a component—it can halt entire systems. Unplanned downtime leads to expensive repairs and even more expensive lost productivity. This is unacceptable for industries relying on continuous operation. As a rule, the larger a motor, the larger the consequences of its failure. This has serious ramifications in heavy industrial applications like pulp/paper processing, steel mills, and cement plants.
How AEGIS Rings Address Bearing Damage
AEGIS® Shaft Grounding Rings offer a practical solution to this problem in motors. These grounding rings provide a low-resistance path from the shaft to the motor frame, and bleed voltage off the shaft before it can build up enough to discharge through the bearings.
The AEGIS SGR is a good choice for smaller motors for grounding rings. We recommend the larger AEGIS PRO Series for larger and medium voltage motors.
AEGIS PRO Rings differ in a few ways from the smaller AEGIS SGR. For one, PRO rings have six circumferential rows of conductive microfibers, as compared to SGRs’ two. These fibers create a 360-degree conductive path around the motor shaft. Unlike other products that use brushes or partial coverage, the AEGIS full-circle design ensures consistent protection. The PRO ring’s extra fiber allows it to carry more current than the two-rowed SGR, to protect higher-power and medium voltage motor bearings.
Manufactured in Mechanic Falls, Maine, AEGIS PRO rings adhere to strict quality standards, including ISO 9001 certification. Their robust construction makes them suitable for a variety of applications, especially in environments where reliability is paramount.
Applications of AEGIS PRO Rings
PRO rings are recommended for:
- Large Frame Low Voltage Motors: 500 HP (375 kW) or greater for intermittent duty, or 300 HP (225 kW) for continuous duty
- Medium Voltage Motors
- DC Motors: 300 HP (225 kW) and higher
- Generators
AEGIS PRO Ring Variants: Finding the Right Fit
Choosing the appropriate AEGIS PRO ring depends on your specific application. The series includes several variants designed to meet different needs. All PRO rings are custom-engineered to fit the destination machine.
AEGIS PROSL
The PROSL is ideal for most large motors operated by, and generators excited by, VFDs. It suits shaft diameters from 2.5 inches to 15.75 inches. Its slim design and flexible installation options make it adaptable to most large motors. The PROSL provides high current capacity, making it effective for heavy-duty applications.
AEGIS PROSLR
For motors operating in harsh environments, the PROSLR offers additional protection. It incorporates an O-ring dust and debris barrier, preventing contaminants from interfering with the microfibers. This is crucial in industries where motors are exposed to dirt, dust, or lubricants. The PROSLR offers consistent performance under severe conditions.
AEGIS PROMAX
The PROMAX is the go-to choice when dealing with the most critical and largest motors. The PROMAX has an even more robust design than the other PRO rings, and is designed for shaft diameters from 15.75 inches to 30 inches. Its robust design makes it suitable for the most demanding situations.
AEGIS PROMR
The PROMR combines the PROSL with a second grounding ring for voltage monitoring. This allows for convenient real-time measurement of shaft voltage. It's a valuable predictive maintenance tool, helping identify potential issues before they lead to failure.
Preserving Your Equipment's Lifespan
Protecting motor bearings from electrical damage is not just about preventing a specific type of wear. It's about ensuring the continuous operation of your systems and avoiding unnecessary costs.
For smaller motors, AEGIS SGRs are a reliable and effective solution. For larger motors, the AEGIS PRO rings will do the job. For more information on selecting the appropriate AEGIS ring for your motor, contact us today.
AEGIS rings also come with a 2-year extended warranty against bearing fluting damage. No other form of shaft grounding comes with 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.
