Failure analysis of three-phase asynchronous motors

Failure analysis of three-phase asynchronous motors

The faults of three-phase asynchronous motors are generally divided into two categories: electromagnetic faults and mechanical faults.

1. Electromagnetic failure Most of the electromagnetic faults occur in the stator winding, such as insulation damage, poor conductor and circuit contact, open circuit, short circuit and wiring error, as well as rotor winding, brushes, starting equipment, fuses, buttons, switches, etc.

2. Mechanical failure Mechanical failures, such as loosening, wear, poor lubrication of bearings, deformation and fracture of end covers, cores, cooling fans, etc.

3. How to distinguish faults When the fault phenomenon exists when the motor is energized and runs, and the fault disappears after the power supply is cut off, it means that it is an electromagnetic fault; If the fault exists when the motor is energized and runs, and the fault still exists after the power supply is cut off, it means that it is a mechanical fault.

2. Failure analysis steps

1. Understand the structure of the motor and the historical data of installation and operation, and inquire about the operation before and after the failure;

2. Check the condition of mechanical parts, such as whether the end cover is broken, whether the shaft is bent, whether the fan is damaged, etc.;

3. Check the condition of the bearing, shake the shaft up and down, left and right, if there is a large looseness or channeling, indicating that there is a problem with the bearing, rotate the rotor vigorously to see whether the rotation is flexible and whether there is any jamming;

4. Check the winding insulation, test whether there is grounding, short circuit or interphase short circuit with a megohmmeter, and measure whether the three-phase DC resistance of the winding is balanced with a double-arm bridge if necessary;

5. Check whether the external wiring has short circuit and open circuit fault, and whether the power supply voltage is normal.

6. If necessary, turn on the motor to check its internal fault.

Failure analysis of three-phase asynchronous motors

The faults of three-phase asynchronous motors are generally divided into two categories: electromagnetic faults and mechanical faults.

1. Electromagnetic failure Most of the electromagnetic faults occur in the stator winding, such as insulation damage, poor conductor and circuit contact, open circuit, short circuit and wiring error, as well as rotor winding, brushes, starting equipment, fuses, buttons, switches, etc.

2. Mechanical failure Mechanical failures, such as loosening, wear, poor lubrication of bearings, deformation and fracture of end covers, cores, cooling fans, etc.

3. How to distinguish faults When the fault phenomenon exists when the motor is energized and runs, and the fault disappears after the power supply is cut off, it means that it is an electromagnetic fault; If the fault exists when the motor is energized and runs, and the fault still exists after the power supply is cut off, it means that it is a mechanical fault.

2. Failure analysis steps

1. Understand the structure of the motor and the historical data of installation and operation, and inquire about the operation before and after the failure;

2. Check the condition of mechanical parts, such as whether the end cover is broken, whether the shaft is bent, whether the fan is damaged, etc.;

3. Check the condition of the bearing, shake the shaft up and down, left and right, if there is a large looseness or channeling, indicating that there is a problem with the bearing, rotate the rotor vigorously to see whether the rotation is flexible and whether there is any jamming;

4. Check the winding insulation, test whether there is grounding, short circuit or interphase short circuit with a megohmmeter, and measure whether the three-phase DC resistance of the winding is balanced with a double-arm bridge if necessary;

5. Check whether the external wiring has short circuit and open circuit fault, and whether the power supply voltage is normal.

6. If necessary, turn on the motor to check its internal fault.

9. The wound motor has a large spark

1) The grade or size of the brush is incorrect.

Repair or replace the brushes.

2) The surface of the collector ring is uneven or there are debris and dirt.

Remove dirt and polish with zero sandpaper.

3) The brush pressure is too small or the pressure is uneven.

Adjust the brush spring pressure.

4) The brush is stuck inside the brush grip.

Grind or replace the brush of the appropriate size and install the brush properly.