Analyze the causes of DC motor heating

It is normal for mechanical equipment to generate heat over a long period of use. When it generates heat, it indicates that the temperature is high, or the mechanical equipment needs to rest for a long time. Mechanical equipment is composed of different accessories. When the product heats, it is also necessary to first understand whether the accessories are heating and what the specific reason is. Next, we will analyze the reasons for the heating of DC motors.

The room temperature is too high; Poor heat dissipation; Overload; Overvoltage, undervoltage, or voltage imbalance; Frequent starting and stopping or frequent forward and reverse rotation; Lack of phase; Fan failure or blocked air inlet and outlet; Lack of oil in bearings; Mechanical jamming and rotor blockage; Excessive load rotational inertia and long starting time; Interturn short circuit; The internal wiring of the new motor is incorrect; There is an error in the star delta wiring; Long restart time for star delta or self coupling voltage reduction starting load or failure to convert normally due to faults; The motor is damp; Broken rotor bar of squirrel cage asynchronous motor; The rotor winding of a wound asynchronous motor is broken or the resistance is unbalanced; Rotor sweeping; Excessive power harmonics, such as large rectifier equipment or high-frequency equipment nearby; The magnetic flux of the iron core of the motor that has been repaired multiple times decreases; Some motors have poor winding process.

When analyzing motor heating faults, use a non-contact infrared thermometer or the temperature measurement gear of a multimeter (with temperature measurement) to measure the temperature of the motor end cover exceeding the ambient temperature of 25 ℃ or above, indicating that the temperature rise of the motor has exceeded the normal range. Generally, the temperature rise of the motor should be below 20 ℃. The direct cause of motor heating is due to high current. The relationship between the motor current I, the input electromotive force E1 of the motor, the induced electromotive force (also known as back electromotive force) E2 of the motor rotation, and the motor coil resistance R is: I=(E1-E2) ÷ R. An increase in I indicates that R decreases or E2 decreases. The decrease in R is generally caused by a short circuit or open circuit in the coil. E2 reduction is generally caused by demagnetization of magnetic steel or by coil short circuit or open circuit. In the maintenance practice of electric vehicles, the method to deal with motor heating faults is generally to replace the motor.

When the DC motor experiences heating in the future, we need to first analyze the specific problem and then adopt corresponding solutions based on the specific problem. Heating of DC motors is a normal thing, and it is important not to rush when encountering problems. Find ways to solve the problem. If it cannot be solved, you can contact professional personnel for consultation.