When the motor current is high, it is often reflected in the serious heating of the motor. The following seven points basically summarize the reasons for the excessive current of the motor. Let's learn about them.
Ⅰ. power supply problem
In terms of power supply, the motor may overheat for the following reasons:
1, the power supply voltage is too high
When the power supply voltage is too high, the electromotive force, flux and flux density of the motor increase accordingly.Since the size of iron loss is proportional to the square of magnetic flux density, the iron loss increases, leading to overheating of the core.The increase of magnetic flux leads to the sharp increase of excitation current component, resulting in the increase of copper loss of stator windings and overheating of windings.Therefore, when the power supply voltage exceeds the motor's rated voltage, the motor will overheat.
2. Too low power supply voltage
When the power supply voltage is too low, if the electromagnetic torque of the motor remains unchanged, the magnetic flux will decrease, the rotor current will increase correspondingly, and the load power supply component in the stator current will increase accordingly, resulting in the copper loss of winding and the overheating of stator and rotor windings.
3. Asymmetric power supply voltage
When the power line is broken in one phase, the fuse in one phase is fused, or the Angle head of the starting equipment is burned so that the one phase is not connected, it will cause the three-phase motor to go single-phase and cause the two-phase winding in operation to overheat through large current and burn out.Therefore, three-phase motor is generally not suitable for fuse protection.
4. Unbalanced three-phase power supply
When the three-phase power supply is unbalanced, the three-phase current of the motor will be unbalanced, causing overheating of the windings.
It can be seen from the above, when the motor overheating, should consider the power supply reasons firstly(soft start, inverter, servo driver can also be considered as power supply).Make sure there is no problem with the power supply before considering other factors.
Ⅱ. Load problem
There are several reasons for the motor to overheat in terms of load:
1. Overload operation of the motor
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, the small horse-drawn cart), which will lead to overheating of the motor.When maintaining the overheating motor, it is necessary to make sure whether the load power is consistent with the motor power, so as to prevent blind and aimless disassembly.
2. The dragging mechanical load is not working normally
Although the equipments matched well, but the drag of the mechanical load work is not normal, the operation of the load is large or small, motor will be overload and heat.
3, the drag of the mechanical failure
When the machinery being dragged is malfunctioning, the rotation is not flexible or stuck, will make the motor overload, resulting in overheating of the motor windings.Therefore, when repairing the motor overheating, the load factor can not be ignored.
Ⅲ. The motor itself
1, motor winding break
When there is a phase winding break in the motor windings or a branch break in the parallel branches, it will lead to unbalanced three-phase current and make the motor overheat.
2, motor winding short circuit
When the motor winding short-circuit fault, short-circuit current is much larger than the normal working current, so that the winding copper loss increased, resulting in winding overheating, or even burn out.
3. Wrong star Angle connection of the motor
When the delta connection motor is wrongly connected into a star and the motor is still running with full load, the current flowing through the stator winding should exceed the rated current and even cause the motor to stop by itself. If the stopping time is a little longer and the power supply is not cut off, the winding will not only seriously overheat, but also burn out.When the star-shaped connection of the motor into a triangle, or a number of coils strung into a branch of the motor into two branches of parallel, will make the winding and core overheating, seriously will burn the winding.
4. Wrong connection of motor coil
When a coil, coil set, or one phase winding is inversely connected, the three-phase current will be seriously unbalanced and the winding will overheat.
5. Mechanical failure of the motor
When the motor shaft bending, assembly is not good, faulty bearing, etc., will make the motor current increase, and copper loss and mechanical friction loss increase, to make the motor overheating.
Ⅳ. Ventilation and heat dissipation
1, the environment temperature is too high, so that the inlet air temperature is high.
2, there are sundries in the air inlet, so that the ventilating air is not smooth, resulting in a small amount of air.
3. Excessive dust inside the motor will affect heat dissipation.
4, fan damage or installed in reverse, resulting in no wind or small air volume.
5. Wind shield is not installed or wind shield board is not installed in the end cover of the motor, resulting in no wind path for the motor.
Ⅴ. repair the motor problem
The starting current of the repaired motor is over 66%, and at the same time, frequent operation of the motor will also result in high current and overheating of the motor.
Ⅵ. Series resistance problem
Winding motor and series resistor do not match, at the same time, the motor work frequently, will also cause high current and the motor overheating.
Ⅶ. Vibration of motor
Excessive motor vibration may also cause high motor current, reasons and treatment:
1. Rotor imbalance -- calibration to ensure balance
2. Belt pulley imbalance or shaft extension and bending -- check and correct
3, motor and load axis is not aligned -- check and adjust the axis of the whole motor
4. Improper motor installation -- check installation and foot screws
5. Sudden overload -- lighten the load
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