In industrial applications, induction motors are widely used in various scenarios such as transportation, processing, HVAC, and automation due to their simple structure, stable operation, and low maintenance cost. However, many users often encounter problems such as serious motor heating or even overload shutdown during operation, which not only affects the life of the equipment, but may also cause production interruptions and operation and maintenance risks.This article will systematically sort out the main causes of induction motor heating and provide corresponding engineering solutions to help equipment procurement personnel, technical managers, and operation and maintenance teams identify problems more scientifically, reduce failure rates, and improve system stability.
Typical manifestations of induction motor heating
The actual manifestations of “heating problems” are that the shell temperature of the induction motor increases, the insulation ages faster, the motor temperature control alarms, and even the thermal relay trips under long-term operation or high-load conditions. To determine whether it is abnormal heating, the following points should usually be combined:
Whether the surface temperature of the motor exceeds the design temperature rise (such as 80K for Class B insulation)
Whether the overheating protection or tripping is frequently triggered
Whether it is accompanied by a decrease in efficiency, unstable speed, difficulty in starting, etc.
If the heating has affected normal operation, the cause should be immediately investigated and improvement measures should be taken.
Analysis of common causes of heating of induction motors
Over-rated operation or excessive load
The undersized induction motor or continuous over-load is one of the primary causes of heating. When the motor is operated at a current exceeding the rated current for a long time, the copper loss rises sharply, the winding temperature rises rapidly, and even insulation breakdown may occur.
Suggestions:
Check the matching relationship between the rated power of the motor and the actual load
Use a clamp meter or inverter data to check whether the long-term operating current exceeds the standard
Upgrade the motor specifications or optimize the load structure if necessary
Abnormal power supply voltage or three-phase imbalance
If the power supply voltage is too high, too low, or the three-phase voltage is unbalanced, the motor will be distorted in the running magnetic field, resulting in aggravated current fluctuations, which will cause serious iron loss and additional copper loss.
Suggestions:
Use a three-phase voltmeter to check whether the power supply voltage is stable
If the power supply fluctuates frequently, consider configuring a voltage stabilizer or using a frequency converter for adjustment
When the three-phase imbalance is greater than 2%, check the power supply system and wiring status
Cooling system failure or ventilation obstruction
If the motor cooling fan is damaged, the ventilation channel is blocked, or the motor installation environment temperature is too high, it will weaken its heat dissipation efficiency and cause heat to be unable to be released in time.
Suggestions:
Clean the motor air duct and fan regularly to ensure that there is no foreign matter blocking
Check whether the fan is running normally and whether the bearing is damaged
When installing, try to avoid the motor being close to the wall, exposed to high temperature or no convection ventilation environment
Frequent start and stop or low-speed heavy-load operation
If the induction motor is frequently started and stopped without a suitable driver, or runs in a low-speed and high-torque state for a long time (such as direct drive, heavy-load start-stop system), the starting current will be amplified, the ventilation efficiency will be reduced, and it is easy to cause overheating.
Recommendations:
For frequent start-stop conditions, variable frequency drive should be used first and reasonable acceleration and deceleration time should be set
If necessary, select a motor model with heat dissipation enhancement structure or temperature control protection
Internal heating caused by winding or bearing failure
If there are problems such as local winding short circuit, bearing jamming, rotor eccentricity, etc. inside the motor, it will cause local overheating or even burning. This is especially common in old equipment that has been in use for more than three years.
Recommendations:
Perform insulation resistance test and winding temperature rise detection regularly
Check bearing lubrication status and replace worn parts in time
If the temperature rise is abnormal but the appearance is normal, consider using infrared thermometer to assist in detecting hot spots inside the winding and end cover
Optimization suggestions in engineering procurement and operation and maintenance
In order to reduce the heating failure of induction motors after the implementation of the project, it is recommended to adopt prevention and control strategies from the source design and selection stage:
Selection stage: reasonably reserve power redundancy (about 10%-20%), especially in heavy load, variable load or outdoor high temperature environment
Drive system: configure inverter operation as much as possible, and reduce heating risk through soft start and frequency control
System integration: pay attention to the ventilation space, ambient temperature and dust and oil prevention measures of the motor installation
Operation and maintenance strategy: establish a regular inspection system, focusing on checking the operation status of bearings, voltage, current and cooling system
The heating problem of induction motors is not caused by a single reason, but the result of multiple factors such as selection, installation, drive, operation and maintenance. For equipment managers and purchasers, understanding the causes behind it and optimizing it from a system engineering perspective is the key to ensuring stable operation of equipment, extending service life and controlling the cost of the entire life cycle.
In a modern manufacturing environment where digitalization and energy saving are equally important, it is recommended that purchasers give priority to motor and controller combinations with intelligent monitoring, temperature control protection and remote diagnosis functions to build a visual and predictable equipment management system.