Types and judgment methods of common faults of electric motors

09/05/2019

Types and judgment methods of common faults of electric motors:

First, the motor can not start
1. The motor does not turn and there is no sound.
The reason is that the motor power supply or winding has two or three phase open circuits. First check if there is a power supply voltage. If there is no voltage in the three phases, the fault is in the circuit; if the three-phase voltage is balanced, the fault is in the motor itself. At this time, the resistance of the three-phase winding of the motor can be measured to find the winding of the phase failure.
2, the motor does not turn, but there is a "beep" sound. Measuring the motor terminal, such as three-phase voltage balance and rated value can be judged as a serious overload.
3, the motor speed is slow and accompanied by "beep" sound, shaft vibration. If the measured phase current is zero, the other two phase currents greatly exceed the rated current, indicating that the phase loss is running. The reason is that the circuit or the power supply is disconnected in one phase or the motor winding is disconnected.

Second, Fuse blown or relay disconnected at startup
1. Troubleshooting steps.
2. Ground fault detection method.
3. Inspection method for winding short circuit fault.
4. Judging method of the tail and tail of the stator winding.


Third, below the rated speed after starting
After the motor starts, there is a "beep" sound and vibration. Check whether the stator winding is disconnected in one phase. The three-phase current balance has a "click" sound but does not vibrate. Check if the three-phase voltage is too low.


Fourth, motor vibration
Disconnect the motor and mechanical transmission and start the motor.


Fifth. There is noise when the motor is running.
The fault occurs when the mechanical part and the electromagnetic part of the motor are distinguished by running the motor first, listening carefully to the sound during operation, and then powering down.
1. Mechanical noise.
(1) Noise emitted by the bearing. It may be that the bearing steel ball is broken and the oil is too small. The inspection method is that the head
of the screwdriver is placed on the outside of the bearing cover, and the ear is attached to the handle. The sound of the "gulugulu" can be approached (the best hollow tube is best, the sound is very clear), indicating that the bearing is faulty.

(2) The noise generated by air friction is very uniform and not strong, which is a normal phenomenon;

(3)The noise caused by the motor broom is "caca" sound. When the newly repaired motor is running, if noise is found, check whether the motor current is balanced, whether the rotation is flexible, and whether the rated speed is reached. If there is no such problem, it may be outside the insulating paper or bamboo wedge protruding slot in the stator slot, causing the rotor to rub with somewhere. Its sound is both sharp and high.
2. Electromagnetic noise.
The rotor and stator do not work well together (generally when new motors are used, or when the same type of motor is interchanged with the rotor). Under normal circumstances, the length of the stator should be slightly longer than the length of the rotor, and the noise is a low hum (or empty sound).
3. The rotor is axially displaced.
Electromagnetic noise is generated and the no-load current is increased, and the electromagnetic performance of the motor is lowered.


Sixth, the motor temperature rise is too high or the winding is burnt
1. The number of positive and negative reversals is too frequent, and the motor often works in the starting state.
2. The driven machine is stuck, the ambient temperature is too high (more than 40 degrees), the belt is too tight, the electromagnetic part is faulty, the power supply voltage is too high or too low, the motor air gap is not uniform, the iron core vent is blocked, and the fan blade Damage, etc.