Five Reasons for Using Electrically Insulated Bearings in Motors

Has your motor encountered these problems?

• Frequent bearing burnouts?
• Unexplained noise or vibration during operation?
• Rising maintenance costs year after year?

TFL Electrically Insulated Bearings provide a system-level solution. They effectively prevent bearing damage caused by shaft currents, extending bearing life by up to 3 times, and maintain an insulation resistance of ≥50MΩ under 1000V, significantly exceeding industry standards.

Eliminate Electrical Erosion for Long-Term Stable Operation

In motor systems driven by Variable Frequency Drives (VFDs), PWM signals generate Common Mode Voltage (CMV), leading to shaft currents that flow through the bearings. Standard bearings cannot withstand these currents, resulting in:

• Electrical erosion on bearing raceways
• Lubricant breakdown
• Fluting damage caused by micro-discharges

Studies show that over 40% of bearing failures in VFD-driven motors are related to electrical leakage. Shaft current damage progresses gradually — it may begin with slight surface roughness, but soon develops into fluting, accompanied by rapidly increasing vibration and noise, eventually causing bearing seizure.

TFL Electrically Insulated Bearings

TFL insulated bearings use high-performance ceramic coatings, such as aluminum oxide (Al₂O₃), which can withstand breakdown voltages up to 1000V and provide insulation resistance exceeding 50MΩ.

For example, the TFL 6216/C3VL0241 model ensures no electrical current passes between bearing components even in harsh electrical environments, completely eliminating the risk of electrical erosion.

Replace high-risk motors (e.g., those with power >75 kW or speed >1500 rpm) with TFL Electrically Insulated Deep Groove Ball Bearings 6216/C3VL0241 for preventive maintenance.

Ceramic Coating and Performance Assurance

Electrically insulated bearings are not simply coated with a layer of paint — they involve advanced precision manufacturing and material science.

Key Features of TFL Insulated Bearings:

• High-Purity Base Material: Made from high-purity GCr15 bearing steel, ensuring dimensional accuracy and long service life.
• Plasma Spraying Technology: TFL uses advanced plasma spraying to evenly and firmly deposit a dense aluminum oxide ceramic layer on the bearing rings. This ensures stable electrical insulation performance with ≥50MΩ insulation resistance and ≥1000V breakdown voltage.
• Dimensional Accuracy & Interchangeability: Despite the added coating, TFL bearings strictly comply with ISO 492 dimension and tolerance standards. All insulated bearings are fully interchangeable with non-insulated types — no motor design modification is required.

TFL insulated bearings can also perfectly replace other brands’ insulated bearings, such as TFL NU324 ECM/C3VL0241 is completely interchangeable with:

• SKF NU 324 ECM/C3VL0241
• FAG NU324-E-XL-M1-J20AA-C3
• NTN 7MC3-NU324EGRB C3
• NKE NU324-E-M6-C3-SQ77

If you are looking for cost-effective electrically insulated bearings, please email info@sdtflbearing.com. Provide the bearing model or dimensions, and we will help you find the most suitable TFL electrically insulated bearing for your application.

Extend Bearing Life, Reduce Maintenance Costs

Electrical erosion caused by shaft currents is one of the leading causes of premature motor bearing failure. Once early bearing damage occurs, operating noise and vibration increase rapidly until the bearing completely seizes. TFL Electrically Insulated Bearings can restore the bearing’s actual service life to its original design life — or even longer.

Unexpected motor downtime leads not only to repair expenses but also to major losses from production interruptions and delivery delays. In highly automated production lines, the failure of a single critical motor can bring an entire line to a halt.

By ensuring long-term stable operation, TFL Electrically Insulated Bearings significantly enhance overall motor reliability — meaning fewer unexpected failures and more predictable maintenance cycles. In high-demand continuous operation fields such as railway traction motors and metallurgical rolling mill drives, the reliability of TFL insulated bearings has been widely proven, ensuring sustained and stable operation of critical equipment.

Each batch of TFL insulated bearings undergoes rigorous dielectric strength and insulation resistance testing to ensure stable long-term performance under rated voltage. All products are 100% tested for insulation performance before delivery, ensuring every bearing meets strict performance criteria.

Multi-Industry Applications: A Stable and Reliable Long-Term Investment

With the growing emphasis on industrial automation and energy efficiency, applications using VFD-driven motors, high-speed motors, and large generators are rapidly increasing — and so are shaft current problems.

Electric Vehicle Drive Systems

As EV battery voltages rise to the 800V high-voltage platform, shaft current leakage becomes more severe. Once current passes through a bearing, it causes electrical pitting, leading to raceway damage, increased vibration, and noise — ultimately shortening the lifespan of both the drive motor and gearbox.

To address this challenge, TFL has developed a high-insulation series of bearings (e.g., TFL 6312M/C3VL0241 Electrically Insulated Bearing) specifically for e-Axle systems. This model features an aluminum oxide ceramic insulation coating covering the outer ring surface and sides, providing ≥1000V insulation resistance, fully meeting — and exceeding — the insulation requirements of 800V EV systems.

Compared with traditional electroplated or painted coatings, TFL’s plasma-sprayed and high-temperature-cured process ensures that the insulation layer does not peel or crack under -40°C to +200°C temperature cycles, while maintaining excellent mechanical adhesion and impact resistance.

Wind Turbine Generators

Wind turbine main generators operate continuously under high humidity and vibration, and converter-driven systems tend to generate high-frequency common mode voltages (CMV). These voltages can cause shaft current leakage, leading to fluting and electrical pitting on bearing raceways — a major source of early motor failure.

For the wind power industry, TFL offers electrically insulated cylindrical roller bearings (e.g., TFL NU324M/C3VL0241). These bearings feature a high-purity aluminum oxide ceramic insulation layer on the outer ring, applied via plasma spraying and precision grinding, delivering ≥100 MΩ insulation resistance and 1000V breakdown voltage.

Compared with grounding rings or carbon brush systems, TFL insulated bearings are compact, maintenance-free, and maintain long-term electrical isolation under complex conditions.

Railway Traction Motors

Rail vehicles powered by high-capacity inverters experience high-amplitude shaft voltages during operation. Conventional bearings are easily damaged under these conditions, leading to raceway arcing, vibration, and premature failure, which directly affect train safety and maintenance cycles.

TFL has developed electrically insulated tapered roller bearings (e.g., TFL 32010X/C3VL0241) specifically for these demanding conditions. This series features an inner ring ceramic insulation coating with enhanced impact resistance and thermal stability, boasting an adhesion strength over 15 MPa and stable insulation performance across -40°C to +180°C.

Variable Frequency Drive (VFD) Systems

Due to PWM modulation characteristics, VFD systems generate shaft voltages and common mode interference currents. These currents cause localized discharge within bearings, leading to lubricant breakdown and surface erosion — one of the most common early failures in industrial motors.

TFL Electrically Insulated Deep Groove Ball Bearings (e.g., TFL 6309M/C3VL0241, 6205M/C3VL0241) are specifically engineered for VFD applications. Their aluminum oxide insulation coating provides ≥50 MΩ insulation resistance and 1000V breakdown voltage, maintaining effective electrical isolation even under high-frequency PWM drive conditions.

Industrial Automation and Machine Tool Spindles

In servo systems and CNC spindle motors driven by high-frequency PWM, shaft currents can disrupt the oil film and cause machining precision drift. Even microamp-level leakage currents can induce micro electrical erosion on raceway surfaces, leading to higher surface roughness and increased noise.

TFL offers custom insulation solutions, including dual-sided insulation coating, ensuring stable electrical isolation for high-speed spindle applications.

Customizable Solutions: Tailored for Every Application

Beyond standard models, TFL provides custom coating upgrades and bearing structure designs based on customers’ existing bearings — delivering optimized insulation performance for every specific industrial application.

Solve Your Bearing Failure Problems

Still troubled by unplanned motor downtime and high maintenance costs? Choose TFL Electrically Insulated Bearings — eliminate the threat of shaft currents at the source and keep your equipment running at maximum efficiency.

As a professional bearing manufacturer from China, TFL is committed to providing:

• A complete range of electrically insulated deep groove ball bearings, cylindrical roller bearings, tapered roller bearings, and spherical roller bearings.
• High-quality ceramic coatings that meet ISO/IEC standards.
• Professional customization services tailored for the most demanding operating conditions.