Common fault diagnosis methods of single-phase motor

1. The power supply voltage is normal, and the motor does not start after power on.

1) The power wiring is open circuit (the motor is completely silent). There shall be no voltage at both ends of the measuring terminal.

2) Open circuit of main winding or auxiliary winding. The open circuit can be determined by measuring the DC resistance.

3) The contact of centrifugal switch is not closed, so that the auxiliary winding cannot be energized. Disconnect the connection point between the main winding and the auxiliary winding, and then determine it by measuring the DC resistance, or by the method in part II.

4) The starting capacitor wiring is open or internally open. The search method is the same as item 3) above.

5) For shaded pole motor, the shaded pole coil (short circuit ring) is open or falls off. For the short-circuit ring, it can be seen from the outside, which can often be found by observation, otherwise it can be determined by the method in the second part.

6) For series excited motor, the brush is not connected or cannot contact the commutator because the brush is too short or stuck, or the brush lead is disconnected, or there is an open circuit in the armature winding and field winding.

2. The power supply voltage is normal. After power on, the motor rotates at low speed, with "buzzing" sound and vibration, and the current does not drop.

1) The load is too heavy.

2) The motor stator and rotor rub against each other. It will make an abnormal friction sound.

3) The bearing is stuck due to poor bearing assembly, oil consolidation in the bearing, bearing roller support or roller damage, etc.

4) For series excited motor, short circuit between commutators or internal short circuit of armature winding, or excessive deviation of brush from the center line (for motor with movable brush).

3. After power on, the power fuse will blow quickly.

1) The winding turns are seriously short circuited to ground. Measure the DC resistance. If the value is far less than the normal value, it is an inter turn short circuit of the winding; In case of serious short circuit to ground, the insulation resistance meter or multimeter can be used with higher resistance (such as R × 1K gear). The current will be greater than the rated value.

2) The outgoing phase line of the motor is grounded. The inspection method is the same as fault item 1).

3) The capacitor is short circuited. Use a multimeter to lower the resistance (e.g. R × Gear 1) measure the DC resistance between the two ends of the starting winding circuit (including capacitor and starting winding, excluding centrifugal switch).

4) Centrifugal switch short circuit to ground. The inspection method is the same as item 1).

5) The load is too heavy. The sound will be abnormal and the current will be greater than the rated value.

4. After the motor is started, the speed is lower than the normal value.

1) The main winding has inter turn or short circuit to ground fault. The inspection method is the same as item 1) in 3.

2) There is a coil reverse connection fault in the main winding. The sound will be abnormal and the current will be greater than the rated value.

3) The centrifugal switch is not disconnected, so that the auxiliary winding cannot be separated from the power supply. The current will be greater than the rated value.

4) Heavy load or bearing damage. The sound will be abnormal and the current will be greater than the rated value.

5) For series excited motor, there is a short circuit between commutators or internal short circuit of armature winding, or the brush and commutator have poor contact.