Analysis of the reasons for the increase in motor failure factors and the selection of protective devices

In modern industrial environments, the increase in motor failure rates is not caused by a single factor, but rather the result of multiple trends and challenges working together.

1、 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

Interturn short circuit and grounding fault: Partial discharge caused by insulation material moisture, aging, or overvoltage breakdown, resulting in winding short circuit or grounding, requires real-time monitoring of insulation resistance and leakage current.   

2、 Selection principles and types of motor protection devices

1. Principles for selecting protective devices

Matching motor capacity and operating conditions: Small capacity motors can choose economical thermal relays, while high-power or critical equipment requires intelligent comprehensive protectors.   

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.   

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.