Wafangdian Bearing Group Corporation (hereinafter referred to as “ZWZ”) recently announced that its project on “high-performance insulated bearings for electric motors” has achieved significant interim results, successfully overcoming core technical bottlenecks in the design, manufacturing, and testing of such bearings. This technology has already been applied in areas including traction motors for rail transit, wind turbine generators, and large-scale industrial variable-frequency motors, providing a self-reliant and controllable supply of critical components for high-end motor equipment.
In high-power motors driven by variable-frequency drives (VFDs), shaft currents act as an “invisible killer” that consistently compromises equipment reliability. When a motor is powered by a VFD, electromagnetic asymmetry between the stator and the rotor generates a shaft voltage. This voltage can break down the lubricating film within the bearings, giving rise to shaft currents that trigger electrical discharge—sparking between the rolling elements and the raceway surfaces—which results in electrical erosion. Such damage drastically shortens bearing lifespan and, in severe cases, can lead to rapid motor failure and unplanned downtime. For equipment such as traction motors in rail transit and wind turbine generators—characterized by high power, high rotational speeds, and long periods of continuous operation—the requirements for bearing resistance against electrical erosion are exceptionally stringent.
For a long time, the market for highly reliable, insulated bearings has been dominated by foreign companies. When domestic equipment manufacturers procure such bearings, they not only face high costs but are also constrained by long lead times and supply chain instability. Through this latest technical initiative, Wafangdian Bearing Group (ZWZ) aims to master the entire process chain—from material formulation to final product testing.
According to project lead Tang Hujiao, the primary technical challenge for insulated bearings lies in the overall performance of the coating: it must provide sufficient insulation strength while simultaneously offering excellent wear resistance and strong adhesion. By developing a proprietary ceramic coating formula and optimizing both the plasma spray gun’s trajectory and the design of the tooling fixtures, the R&D team achieved a continuous, uniform, and highly dense coating on the surface of the bearing’s outer ring. Furthermore, the team developed a high-precision, low-damage grinding process for the insulating coating, effectively overcoming the industry-wide challenge of micro-crack formation during subsequent machining. These technological breakthroughs have enabled the transition of insulated bearings from the laboratory to mass production.
In the realm of testing and service-life assessment, Wafangdian Bearing Group (ZWZ) has pioneered the development of an accelerated life model for insulated bearings based on combined electrical and mechanical stress—a first in China. While traditional bearing life tests account only for mechanical loads, insulated bearings in actual operation are subjected to the combined effects of both electrical and mechanical stress, resulting in more complex failure mechanisms. ZWZ’s independently developed accelerated testing equipment can simulate the actual, extreme operating environments these bearings face; by applying precisely controlled electrical and mechanical loads, it enables an accurate prediction of the end of a bearing’s service life. The establishment of this model provides a quantitative basis for evaluating the reliability of insulated bearings and serves as a foundation of data for future product iterations.
Currently, this technological achievement has been applied across several fields. In rail transit, insulated bearings are used in traction motors, helping to reduce the risk of premature bearing failure caused by shaft currents. In the wind power sector, the variable-frequency drive systems of high-capacity wind turbines impose similarly stringent requirements for bearing insulation. In the realm of large-scale industrial variable-frequency motors, this technology offers a domestically produced solution for high-voltage motors used in industries such as metallurgy, mining, and petrochemicals.
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