Dongguan Langyi Electromechanical Technology Co., Ltd.


Motor heating cause analysis

[Guide] During the use of the motor, it often occurs that its own operating temperature rises, or even fails to work. There are many reasons for the motor to heat up. Today, Ms. See the actual communication

1. The motor is overheated due to power supply

● The power supply voltage is too high. When the power supply voltage is too high, the back-EMF, magnetic flux, and magnetic flux density of the motor increase. Because the iron loss is proportional to the square of the magnetic flux density, the iron loss increases, causing the core to overheat. The increase of the magnetic flux causes the component of the exciting current to increase sharply, resulting in increased copper losses in the stator windings and overheating the windings. Therefore, when the power supply voltage exceeds the rated voltage of the motor, the motor will overheat.

● The power supply voltage is too low. When the power supply voltage is too low, if the electromagnetic torque of the motor remains unchanged, the magnetic flux will decrease, and the rotor current will increase accordingly. The load power component in the stator current will increase accordingly, causing the winding copper loss to increase, resulting in overheating of the stator and rotor windings. .

● The power supply voltage is not symmetrical. When the power line is disconnected from one phase, it will cause single-phase operation of the three-phase motor, resulting in overheating of the two-phase windings running through high current, which will cause the motor to burn out. It is often said that the motor is damaged due to lack of phase.

● The three-phase power supply is unbalanced. When the three-phase power supply is unbalanced, the three-phase current of the motor will be unbalanced, and zero-sequence and negative-sequence currents will flow in the motor windings, causing the windings to overheat.

When the motor is overheating, the exclusion method should be adopted, and the cause of the power supply should be considered first.

2. Load problem causes the motor to overheat

● The motor is overloaded. When the equipment is not matched and the load power of the motor is greater than the rated power of the motor, the motor will be overloaded for a long time (that is, a small horse-drawn cart), which will cause the motor to overheat.

When repairing overheated motors, you should first find out whether the load power matches the motor power to prevent blind disassembly.

● The mechanical load being dragged is not working properly. Although the equipment is matched, the mechanical load being dragged is not working properly, and the load is large and small when running. For example, if the motor is equipped with a thresher, when the feeding amount is too large, the motor will generate heat due to overload.

● The mechanical failure of the drag. When the machine being towed is faulty, inflexible or stuck, it will overload the motor and cause the motor winding to overheat.

3. The motor itself causes overheating

● The motor winding is open. When one phase of the motor winding is disconnected or one of the parallel branches is disconnected, the three-phase current will be unbalanced and the motor will overheat.

● When the motor winding has a short-circuit fault, the short-circuit current is much larger than the normal working current, which increases the copper loss of the winding, causing the winding to overheat and even burn out.

● The motor connection is incorrect. When the delta-connected motor is connected in a star shape by mistake, if the motor is still running at full load, the current flowing through the stator windings must exceed the rated current, and even cause the motor to stop by itself. If the stall time is longer and the power is not cut off, the winding not only Severe overheating can also burn the motor.

When a star-connected motor is misconnected into a triangle, or a number of coils are connected in parallel to form a branch, a motor is misconnected into two branches in parallel, which will overheat the winding and the iron core and burn the winding in severe cases.

● Motor process wiring. When a coil, a group of coils or a phase winding is connected reversely, the three-phase current will be severely unbalanced and the winding will overheat.

● Mechanical failure of the motor. When the motor shaft is bent, poorly assembled, and the bearing is faulty, it will increase the motor current, increase copper loss and mechanical loss, and cause the motor to overheat.

4. Poor ventilation and heat dissipation cause the motor to overheat

● The ambient temperature is too high and the inlet air temperature is high.

● The air inlet is blocked by debris, which makes the air intake not smooth, resulting in a small air intake.

● Too much dust inside the motor affects heat dissipation.

● The fan is damaged or installed backwards, causing no wind or small air volume.

● The windshield is not installed or the windshield is not installed in the motor end cover, resulting in no proper air path for the motor.

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Record nuber Gangdong ICP NO :17115209