What Is a Motor Shaft Grounding System?
A motor shaft grounding system—commonly referred to in the industry as a shaft grounding brush or shaft grounding ring (shaft earthing brush or shaft earthing ring outside of the U.S.)—is a crucial motor protection component that mitigates Variable Frequency Drive (VFD)-induced shaft voltage. The stray voltage, if not properly redirected, causes current to discharge through the bearings leading to electrical discharge machining (EDM). EDM causes bearing damage such as pitting, fluting, and eventual bearing failure.
Grounding systems use conductive brushes or fibers to create a lower-resistance path for unwanted electrical current to flow safely to ground. When properly designed and installed, they extend motor life, reduce downtime, and prevent costly repairs.
The Problem: Shaft Voltage & Bearing Failure
VFDs are now commonly used for controlling motor speed and energy use—but they also introduce high-frequency electrical voltages that build up on the motor shaft. If this shaft voltage is high enough then current discharges through the bearings leading to:
- Microscopic pitting on the bearing surface
- Fluting and bearing noise
- Lubrication breakdown
- Premature bearing failure
Without a reliable grounding system, these problems are almost guaranteed—especially in high-speed or continuous-duty industrial environments.
Why Choose Helwig’s BPK™ Shaft Grounding System?
Exceptional High-Frequency Performance
The Bearing Protection Kit (BPK)™ system features a proprietary silver graphite brush with extremely low electrical resistance, allowing it to safely redirect the high-frequency currents generated by VFDs. Unlike carbon fibers, performance stays consistent throughout the life of the grounding kit.
10+ Years of Life – Typically Outlasts Motor – Proven Durability
Helwig’s BPK™ is built to last well over a decade, maintaining shaft voltage below 1V peak-to-peak and protecting bearings long-term—even in dirty or contaminated environments. BPKs have been successfully used in the field for more than 30 years.
Maintenance-Free Operation
With the Helwig BPK there’s no need to paint silver epoxy on the shaft and servicing is not required. The silver graphite brush is self-cleaning, removing oxidation and contaminants from the shaft to ensure reliable contact and conductivity.
Simple Installation, Minimal Inventory
The EZ MultiFit® bracket system allows for fast installation without uncoupling motors. A single BPK™ model fits a broad range of shaft sizes—reducing SKUs and streamlining your inventory.
Why Other Grounding Solutions Fail
Carbon Fiber Rings: Short-Term Fixes
At first, carbon fiber rings can reduce shaft voltage. But within 6–12 months, the performance drops as the bristles degrade and resistance rises.
- Higher resistance materials result in weaker grounding
- Aluminum housings are less effective in high-frequency applications
- Ongoing maintenance required – silver paint needed every 6–12 months
- Short lifespan leads to more downtime and more replacement cycles
Imitations: Poor Engineering, Inferior Results
Generic knockoffs attempt to mimic the BPK™, but inferior materials and flawed design and manufacturing lead to poor performance:
- Excessive spring pressure causes premature brush wear
- Concave brush designs limit shaft contact
- Less effective brush material increases resistance and friction
- Malleable brackets are difficult to install and not suitable for industrial applications
Bottom line: If it’s not a Helwig BPK™, it’s not engineered to last.
BPK™ vs. Carbon Fiber Grounding Ring Comparison Chart
Frequently Asked Questions
What does a shaft grounding system do?
It redirects VFD-induced shaft discharges away from the motor bearings to prevent EDM damage like pitting, fluting, and burnt grease, and extends motor life.
How is Helwig’s grounding system different?
Helwig’s BPK™ uses silver graphite brushes, not carbon fibers, offering better conductivity, longer lifespan, and zero maintenance.
Can the BPK™ system be added to existing motors?
Yes. The EZ MultiFit® bracket makes retrofitting fast and non-invasive. BPKs can be installed on the drive and non-drive end, radially or axially.
Does it require ongoing maintenance?
No. Helwig’s BPK™ is self-lubricating and built for maintenance-free operation—even in contaminated environments.
Protect Your Bearings with the Best Grounding System Available
Don’t risk your equipment with short-lived or inferior shaft grounding solutions. Choose Helwig’s BPK™—the industry’s most durable, maintenance-free shaft grounding system—and eliminate shaft voltage problems for good.