Variable Frequency Drives (VFDs) are now standard equipment in manufacturing facilities, where precise motor speed control, process optimization, and energy efficiency are central to competitiveness. From process pumps to high-capacity conveyors, VFDs enable operators to match output to demand, reduce energy costs, and improve overall system performance.
Yet with these benefits come a well-documented reliability challenge: electrical bearing damage caused by shaft voltage. Without proper protection, this failure mode shortens motor life, increases maintenance costs, and leads to unplanned downtime—outcomes no manufacturer can afford.
The Reliability Risk in VFD-Driven Motors
VFDs generate a high-frequency common-mode voltage that couples onto motor shafts. In the absence of a safe discharge path, this shaft voltage seeks the path of least resistance — often through the motor bearings. The resulting electrical discharge machining (EDM) creates pitting and fluting on the bearing raceways, which accelerates wear and ultimately causes premature failure.
The consequences are significant:
- Unexpected costs of motor repair or replacement
- Production delays caused by motor outages
- Lost revenue from downtime
Best Practices for Bearing Protection in Manufacturing Applications
To mitigate shaft voltage damage, the following practices are recommended:
- Adhere to manufacturer guidance: Always follow drive manufacturer's recommendations for VFD setup and grounding practices.
- Install AEGIS® Shaft Grounding Rings: A properly mounted grounding ring provides a low-impedance path for harmful shaft voltage to safely discharge.
- Select appropriate mounting methods: Options include solid and split rings, secured by clamps or conductive epoxy, solid and split uKITs with universal mounting brackets, and bolt-through designs.
- Enhance shaft conductivity: Applying a conductive shaft coating improves the shaft-ring electrical interface and helps maintain long-term performance.
- For motors over 100 HP: Best practice is to isolate one bearing and install an AEGIS® Shaft Grounding Ring on the opposite end to ensure complete protection.
The effectiveness of any shaft grounding solution depends on proper installation. A well-installed ring provides years of bearing protection, whereas a poorly installed ring may offer little benefit.
Why AEGIS Rings Are the Industry Standard
AEGIS Shaft Grounding Rings have become the benchmark for VFD-driven motor bearing protection across manufacturing environments. Engineered with 360° circumferential microfibers, they deliver continuous shaft contact to safely bleed voltage away from bearings.
Key advantages include:
- Virtually frictionless operation with a lab-tested wear life of up to 200,000 hours
- Low-to-no maintenance once installed
- Proven reliability across diverse motor sizes and industrial environments
- Broad range of designs to accommodate new equipment and retrofit applications
For real-world applications, explore: AEGIS Applications
FAQs: Shaft Grounding for Manufacturing
Q: Do all VFD-driven motors in manufacturing require shaft grounding?
A: Yes. Any VFD-controlled motor is at risk of shaft voltage discharge. Grounding rings are a preventive measure to avoid bearing damage.
Q: What’s the best practice for motors over 100 HP?
A: Isolate one bearing and install an AEGIS Shaft Grounding Ring on the opposite end for maximum protection.
Q: Can shaft grounding rings be retrofitted to existing motors?
A: Yes. Split rings, clamp-on designs, and epoxy kits make it possible to retrofit AEGIS rings to motors already in service. However, AEGIS rings only protect against future damage - they cannot undo damage that’s already occurred.
Protecting Manufacturing Assets Before Failure Happens
For manufacturers, the question is not whether VFDs will be used — they are an industry standard — but how to mitigate the unintended reliability risks they introduce. Installing shaft grounding rings is one of the most effective and practical steps for preventing electrical bearing damage.
By combining VFD-enabled efficiency with proven shaft grounding, facilities can achieve the performance they expect without sacrificing uptime.
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.
