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Why Do Electric Motor Bearings Leak Electricity? (Causes & Prevention Tips) Have you ever wondered why electric motor bearings fail prematurely despite proper lubrication and regular maintenance? One often overlooked cause is bearing current leakage, also known as electric motor bearing leakage or shaft voltage discharge. When stray electrical current passes through the bearings instead of the intended path, it can cause significant damage — including pitting, fluting, noise, vibration, and even complete motor failure. In this article, we’ll explore: What causes bearing current in electric motors How to identify early signs of damage Practical strategies to prevent future failures Let’s get started. What Is Bearing Current Leakage? Bearing current leakage occurs when unintended electrical current flows through the motor’s bearings rather than staying within the designed electrical circuit. This phenomenon typically happens due to imbalances in the magnetic field or high-frequency voltages generated by variable frequency drives (VFDs). Over time, these currents create microscopic arcing between the bearing components. This leads to surface damage such as pitting and fluting — a repetitive groove-like erosion pattern on the bearing raceway. Eventually, this damage results in increased noise, vibration, and premature bearing failure. Common Causes of Bearing Current Leakage 1. Moisture and Water Intrusion Humid environments or exposure to water can degrade internal insulation and wash away protective lubricants. As a result, electricity may find a new path — often through the bearings. Tip: Use sealed bearings and ensure appropriate motor enclosures for wet or outdoor applications. 2. Oil, Grease, and Dirt Buildup Contamination from oil, dust, or debris on motor windings reduces their insulation performance. This allows stray current to escape and travel through the bearings to ground. Tip: Clean motor internals regularly and use non-conductive, high-quality grease. 3. Damaged Wire Insulation Cracked or aged insulation on power cables — especially near terminal boxes or where wires enter the motor housing — creates a direct path for current leakage. Tip: Conduct regular visual inspections and insulation resistance tests. 4. Overheating and Aging Prolonged operation under high temperatures accelerates the aging of insulation materials. Once insulation breaks down, it no longer contains the electrical current effectively. Tip: Monitor motor temperature and avoid long-term overloading. How to Prevent Bearing Current Leakage Here are some practical steps you can take to extend the life of your electric motors and reduce unplanned downtime: 1. Keep Motors Dry Use proper sealing and ventilation to minimize moisture buildup. Store motors in dry environments and choose appropriate enclosures based on operating conditions. 2. Clean Windings Regularly Remove conductive contaminants from windings and internal components during scheduled maintenance. This helps maintain good insulation properties. 3. Inspect Wiring Routinely Check all wiring connections and insulation for wear or damage. Replace any faulty cables or terminals immediately. 4. Manage Heat and Wear Avoid motor overloading and ensure cooling systems are functioning properly. Older motors or those used in harsh environments are more prone to insulation breakdown. 5. Install Shaft Grounding or Use Insulated Bearings In high-risk applications, install shaft grounding rings or use insulated bearings to redirect stray currents safely to ground, bypassing the bearings entirely. Expert Tip: If you suspect bearing current issues, consult with a qualified motor technician or maintenance specialist for a professional diagnosis. The Cost of Ignoring Bearing Current Allowing bearing current to go unchecked can lead to costly consequences: Increased maintenance and repair costs Unplanned production downtime Safety risks due to unexpected motor failure By understanding the root causes — such as moisture, contamination, insulation failure, and aging — you can take proactive steps to protect your equipment and improve operational efficiency. Final Thoughts Preventing electric motor bearing leakage starts with regular inspection, proper maintenance, and awareness of your electrical system's health. Whether you're managing a single motor or an entire industrial facility, addressing these issues early can significantly reduce repair costs and prolong equipment life. If you’re experiencing frequent bearing failures or suspect electrical leakage, don’t wait — reach out to our team of motor experts today for a professional diagnosis and customized solution. Want More Technical Insights? Subscribe to our newsletter or follow our blog for more in-depth guides on motor maintenance, troubleshooting, and industrial best practices.

Choosing the Right Bearings for Your Electric Motors Motor bearings may be small, but they play a big role in keeping industrial motors running smoothly. One of the most important factors in bearing performance is how well it handles heat. Exceeding temperature limits can lead to early failure, costly downtime, and reduced motor efficiency. In this article, we’ll walk through the key points engineers and maintenance teams should know when selecting bearings for electric motors. 1. Heat Stabilization Treatment Temperature (HSTT) Bearing steel isn’t just strong — it’s specially treated to hold its shape and strength under heat. This treatment sets a limit known as the Heat Stabilization Treatment Temperature (HSTT). If the bearing runs hotter than its HSTT, it can lose hardness and change shape slightly. These changes can cause vibration, noise, and shorten the life of the bearing. Different types of bearings (like deep groove, angular contact, or cylindrical roller) and different brands have different HSTT ratings. Always check the manufacturer's datasheet for exact values. 2. Standard vs. High-Temperature Bearings Most standard motor bearings are built for normal conditions: Usual range: -30°C to +120°C (-22°F to +250°F) But some applications — like high-speed spindles, furnace fans, or motors in hot environments — need more protection. For these, choose high-temperature (HT) bearings, which are made to handle temps above 120°C (250°F), sometimes up to 200°C (392°F) or higher. 3. Don’t Overlook Cages & Seals Even if the steel can take the heat, the cage and seal materials might not. Common Cage Materials: Steel / Stainless Steel: Good for high temperatures (up to 150°C+) Brass: Similar high-temp performance Polyamide (PA66): Cost-effective but only good up to around 120°C — avoid it in hot-running motors Seal Options: NBR (Nitrile Rubber): Standard choice, works well from -30°C to +120°C FKM (Viton® type): Better for high temps, from -20°C to +200°C PTFE and other polymers: For extreme conditions with high heat or chemicals 4. Grease Matters More Than You Think Grease keeps the bearing running smoothly, but it reacts strongly to temperature. Too hot: Grease gets runny, leaks out faster, and loses protection Too cold: Grease thickens, making startup harder and reducing lubrication When choosing grease: Check viscosity at your operating temp Make sure the dropping point is well above your max temp Pick one with good oxidation resistance Plan for re-lubrication intervals, especially in hot environments 5. How to Choose the Right Bearing To avoid failures, follow these steps: ✅ Measure actual bearing temperature, not just ambient or motor surface ✅ Pick a bearing with HSTT higher than your max operating temp ✅ Check cage and seal materials match your thermal needs ✅ Use the right grease for your temp range ✅ Use cooling methods if needed — like airflow or cooling jackets Why It All Matters Getting bearing temperature limits wrong can lead to: Early bearing failure Increased maintenance costs Vibration and noise Safety risks Lower energy efficiency Choosing the right motor bearing is about more than size and load rating. Temperature tolerance is a core design factor that affects reliability, uptime, and long-term performance. If you're building or maintaining motors where precision and stability are critical — like in automation, robotics, or high-speed machining — make sure your bearings are up to the thermal challenge. Torque Accuracy. Spindle Stability. Beining Technology. High-performance motor bearings designed for reliable operation across a wide temperature range.

  モーターベアリングは、電気機械システムの縁の下の力持ちです。その性能と寿命を決定する上で、見過ごされがちな重要なパラメータの1つが、ベアリングクリアランスです。これは、もう一方のリングを固定した状態で、クランプされていない内輪または外輪の半径方向または軸方向の測定された動きのことです。 クリアランスの理解：ラジアル vs. アキシャル ラジアルクリアランス：シャフト軸に垂直な動き。 アキシャルクリアランス：シャフト軸に平行な動き（通常、ラジアルよりも小さい）。 この測定された隙間は、無負荷状態で取り付け前に存在し、リングと転動体の製造公差を考慮した平均的な動きを表します。 ベアリングクリアランスが重要な理由：性能と寿命への影響 適切なクリアランスを選択することはオプションではなく、モーターの健全性の基本です。 クリアランスが少なすぎる（過度にタイト）：運転中に過度の摩擦と熱の蓄積を引き起こします。最悪の場合？壊滅的な故障（ベアリングの焼き付き「高温ロックアップ」）により、ベアリングが破壊され、モーターが損傷する可能性があります。 クリアランスが多すぎる（過度にルーズ）：転動体の過度の内部運動を許容し、振動、騒音、不均一な負荷分散、摩耗の加速、そして最終的にはベアリングとモーターの早期故障につながります。 クリアランスのバランス：最適な性能への鍵 モーターの設計と製造における正確なクリアランス制御は不可欠です。これは直接的に以下を決定します。 運転安定性：スムーズな回転のために振動を最小限に抑えます。 温度管理：危険な過熱を防ぎます。 負荷分散：転動体への均一な応力を確保します。 長寿命：ベアリングとモーター全体の耐用年数を大幅に延長します。 エンジニアと購入者にとっての結論 最適な内部クリアランス（熱膨張に対応する必要がある電気モーターではC3と指定されることが多い）を備えたモーターベアリングを選択することが重要です。これは、信頼性の高い動作を実現し、ダウンタイムを最小限に抑え、モーター駆動システムの投資収益率を最大化するための基礎となります。 トルク精度、スピンドルの安定性 – ベアリングから始まります。精密さを選択してください。 Beining Technology – 重要なモーターベアリングソリューションの専門知識