The correct method of the motor current is too high

Power problem

1, the power supply voltage is too high

When the power supply voltage is too high, the motor back electromotive force, magnetic flux and magnetic flux density increase. Since the magnitude of 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 excitation current component to increase sharply, which causes the copper loss of the stator winding to increase and the winding to overheat. Therefore, when the power supply voltage exceeds the rated voltage of the motor, the motor will overheat.

2, 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, the rotor current will increase accordingly, and the load power component will increase in the stator current, causing the copper loss of the winding to increase, resulting in a stator and a rotor. The winding is overheated.

3, the power supply voltage is asymmetrical

When the power line is disconnected, the fuse is blown, or the corner of the blade is burned, causing a phase failure, the three-phase motor will go single-phase, causing the running two-phase winding to overheat through a large current and burn it. Therefore, fuses are generally not protected for three-phase motors .

4, three-phase power imbalance

When the three-phase power supply is unbalanced, the three-phase current of the motor is unbalanced, causing the winding to overheat.

It can be seen from the above that when the motor overheats, the power supply should be considered first ( soft start, inverter, servo drive can also be regarded as power ). After confirming that there is no problem with the power supply, consider other factors.

Power problem

1, motor overload operation

When the equipment is not matched and the load power of the motor is greater than the rated power of the motor, the long-term overload operation of the motor (ie, the small horse-drawn cart) will cause the motor to overheat. When repairing the overheated motor, first check whether the load power matches the motor power to prevent blind and unintentional disassembly.

2. The mechanical load of the drag is not working properly.

Although the equipment is matched, the mechanical load dragged is not working properly. When the load is large, the load is large and the motor is overloaded and generates heat.

3, the dragging machinery is faulty

When the machine being dragged is faulty, the rotation is inflexible or stuck, it will overload the motor and cause the motor winding to overheat. Therefore, when the motor is overheated, the load factor cannot be ignored.

Motor itself problem

1, motor winding open circuit

When one phase winding in the motor winding is broken, or one branch in the parallel branch is open, the three-phase current will be unbalanced and the motor will overheat.

2, motor winding short circuit

When the motor winding has a short-circuit fault, the short-circuit current is much larger than the normal operating current, which causes the winding copper loss to increase, causing the winding to overheat or even burn out.

3, motor star angle connection error

When the delta connection motor is staggered into a star shape, the motor is still running at full load, the current flowing through the stator winding exceeds the rated current, and even the motor stops by itself. If the stall time is longer and the power is not cut off, the winding is not only serious. Overheating will also burn out. When the star-connected motor is misaligned into a triangle, or a plurality of coils are connected in a branch, the motor is misconnected into two branches in parallel, which will overheat the winding and the core, and will burn the winding in severe cases.

4, motor coil connection error

When a coil, coil set or one-phase winding is reversed, it will cause a serious imbalance of the three-phase current and overheat the winding.

5, the mechanical failure of the motor

When the motor shaft is bent, the assembly is not good, the bearing is faulty, etc., the motor current is increased, the copper loss and the mechanical friction loss are increased, and the motor is overheated.

Ventilation and heat dissipation

1. The ambient temperature is too high, so the inlet air temperature is high.

2. There are debris in the air inlet to block the air, which makes the air intake small.

3. Excessive dust inside the motor affects heat dissipation.

4. The fan is damaged or reversed, resulting in no wind or small air volume.

5, no windshield or motor end cover is not equipped with windshield, resulting in no motor wind path.

other problems

1. Rework motor problem

The motor starting current of the repaired motor is more than 66%, and the motor is frequently operated, which also causes high current and overheating of the motor.

2. Series resistance problem

Wire-wound motors and series resistors do not match, and the motor operates frequently, causing high currents and overheating of the motor.

3. Motor vibration problem

Excessive motor vibration may also cause high motor current, reasons and treatment methods:

1. Rotor imbalance - leveling balance

2, pulley imbalance or shaft extension bending - check and correct

3. The motor is not aligned with the load axis - check the axis of the unit

4, the motor is not properly installed - check the installation and foot screws

5, the load suddenly overweight - reduce the load