一、Reasons for the increase in motor failure factors:
1.Deterioration of power quality, voltage fluctuations, and three-phase imbalance: The complexity of power grid loads (such as the integration of new energy and the increase of nonlinear equipment) leads to voltage amplitude fluctuations exceeding the limit (± 5%) and three-phase imbalance exceeding the limit (>5%), causing motor overcurrent, heating, and efficiency decline. Phase loss operation: Aging or poor contact of distribution lines can easily lead to phase loss. When there is a phase loss, the remaining two-phase current suddenly increases to 4-7 times the rated value, accelerating insulation aging and even burning out windings.
2.Mechanical and environmental factors: Bearing wear and rotor imbalance: Long term high load operation or insufficient lubrication can cause bearing abnormal noise and jamming, and rotor imbalance can exacerbate vibration, affecting motor life. Poor heat dissipation: Dust accumulation, blocked ventilation ducts, or high temperature environments can lead to a decrease in heat dissipation efficiency, resulting in excessive temperature rise of the winding (such as halving insulation life for every 10 ℃ increase).
3.Complex operating conditions, frequent start stop and overload: Modern equipment requires higher start stop frequency and dynamic response of motors, and frequent surge currents (up to 6-8 times the rated current) lead to thermal fatigue accumulation. Diversified load types: Abnormal loads such as pump idling and fan stalling exacerbate mechanical stress on the motor, requiring more precise protection logic response.
4.Insulation aging and electrical faults, inter turn short circuits, and grounding faults: Insulation materials may become damp, aged, or cause partial discharge due to overvoltage breakdown, resulting in winding short circuits or grounding. Real time monitoring of insulation resistance and leakage current is required.
二、Selection principles and types of motor protection devices
1.Principle of selecting protective devices to match motor capacity and operating conditions: For small capacity motors, economical thermal relays can be selected, while for high-power or critical equipment, intelligent comprehensive protectors should be used. Comprehensive functional coverage: It needs to cover core fault types such as overload, phase loss, locked rotor, imbalance, and leakage, and support multi parameter monitoring (current, voltage, temperature). Anti interference and reliability: In industrial environments, EMC standards (such as GB/T17626) must be met, and industrial grade components must be used to ensure high/low temperature stability.
2.Common types and applicable scenarios of protective devices
（1）Thermal relay: Low cost, reliable overload protection, but low sensitivity of phase loss protection and no real-time monitoring function. Trial scenario: Ordinary low-power motor, non frequent start stop environment
（2） Electronic overcurrent relay: supports inverse time characteristic, wide setting range (3-4 times In), and can display fault type. Trial scenario: occasions with large load fluctuations such as mines and compressors.
（3） Intelligent comprehensive protector: integrates protection, monitoring, and communication functions, supports Modbus protocol, and can record historical fault data. Trial scenarios: Key equipment, automated production lines
（4） Temperature detection type protector: directly monitors the winding temperature (such as PTC thermistor) to avoid hysteresis of current protection. Trial scenario: Submersible pumps and compressors with high-precision temperature control requirements
3. Protection scheme under special working conditions
High voltage/high-frequency environment: differential protection (such as 9698 generator differential device) is used to prevent stator winding phase to phase short circuit. Flammable and explosive environment: Use explosion-proof protectors and combine residual current monitoring (30mA threshold) to prevent electric leakage fires. Long distance power supply line: equipped with low voltage protection (0.5-0.7Un action) to avoid insufficient torque caused by undervoltage operation.
三、 Development trend of protective devices
1. Intelligentization and integration: predict faults through AI algorithm (such as bearing wear trend analysis), and realize local decision-making by combining edge computing.
2. High precision sensing technology: using Roche coils or fiber optic current sensors to improve sampling accuracy (± 0.5%), suitable for complex harmonic environments powered by frequency converters.
3. Cloud platform linkage: Supports 4G/5G remote monitoring, real-time uploading of data to the cloud for energy efficiency analysis and health management.
四、Summary
The increase in motor failures is the result of the combined effects of power supply quality, mechanical load, and environmental factors, and it is necessary to select suitable protective devices based on specific operating conditions. Traditional thermal relays are still suitable for simple scenarios, while intelligent integrated protectors have become the mainstream trend with their multifunctional integration and communication capabilities. In the future, the combination of predictive maintenance and IoT technology protection solutions will further enhance the reliability of motor systems.
Post time: Sep-30-2025