Protecting Motor Bearings: Starting with Eliminating Shaft Currents

Have you ever been puzzled and frustrated by unexplained bearing failures, abnormal noise, and unplanned downtime in your motors, fans, or pumps? Even after replacing with high-quality bearings and enhancing lubrication maintenance, the problems still recur prematurely. Behind this, a hidden killer of modern industry, known as "bearing electro-corrosion," is likely lurking – shaft current.

In today's industrial landscape, where variable frequency drive (VFD) technology is widely used to improve energy efficiency and control, a related problem has emerged: the high-frequency PWM voltage generated by VFDs can easily induce shaft voltages of up to tens of volts on the motor shaft. Once this voltage breaks down the thin bearing oil film, instantaneous pulse currents will pass through the precision bearing raceways.

This damage is silent but sufficient to cause expensive bearings to fail completely within just a few months. The surface will be etched with washboard-like pits by electrical sparks, the lubricating oil will rapidly carbonize, ultimately leading to soaring equipment vibration, excessive temperature, and unplanned downtime. Each unexpected shutdown means huge production losses and high maintenance costs.

Faced with this challenge, the industry has tried various solutions. While using insulated bearings can block the circuit, it cannot discharge the accumulated charge on the shaft and is expensive; traditional grounding carbon brushes suffer from rapid wear, easy contamination, and frequent maintenance, often resulting in reduced effectiveness due to poor contact.

This is where the value of modern high-performance shaft grounding rings lies. It's not just a simple component, but a complete shaft current management system. Its core principle is to maintain continuous, stable, low-impedance contact with the rotating shaft through specially designed precious metal fiber bundles, actively creating an optimal "discharge channel" for harmful shaft currents and common-mode currents.

This preferential path safely guides the shaft current to the ground, completely preventing the current from flowing through the bearings. Advanced shaft grounding rings feature a zero-wear design and adaptive structure, maintaining ultra-low contact resistance in the milliohm range for extended periods without maintenance, completely solving the inherent drawbacks of traditional carbon brushes.

Volsun has been deeply involved in the field of motor bearing protection for many years. Based on a profound understanding of the mechanisms of bearing electrical erosion, we provide customized shaft current protection solutions – shaft grounding rings – to customers in numerous industries worldwide. From heavy-duty transmissions in mining equipment to precision generators in wind turbines, from chemical process pumps to high-speed machine tool spindles, our shaft grounding rings consistently protect the core components of equipment, reducing maintenance and replacement costs, thanks to their long-lasting, maintenance-free operation, extremely low contact resistance, and excellent environmental adaptability.

Currently, the Volsun shaft grounding ring series has evolved to its third generation.  Improvements in process and structure have made the product more competitively priced, and we have established deep collaborations with 70% of the mainstream new energy vehicle manufacturers in China.