The common failure and treatment of DC motor

1. Cannot start

1) The power is not connected.

Use a multimeter to check the connection and contact conditions of the power supply lines and electrical switches to make them connected and in good contact.

2) The lead wire of the motor is short-circuited or grounded.

Check and deal with the short circuit between the lead wires and the ground fault to the base.

3)The brushes are in poor contact with the commutator.

Check the contact between the brush and the commutator, and observe whether the brush is stuck in the brush holder and cannot slide freely, or the contact surface is too small.

4) The motor is overloaded.

Reduce motor load.

5) There is a short circuit or open circuit fault in the excitation winding.

Check and measure the field winding, find out the short circuit or open circuit point for repair.

6) The polarity of some main magnetic poles is reversed, so that the main magnetic flux is partially offset.

Check the polarity of the main magnetic pole coil of the excitation winding, find out the wiring error and correct it.

7) There is an open circuit fault in the armature winding circuit.

Use a multimeter or resistance meter to measure the resistance of the armature winding circuit, as well as the resistance of the commutation winding and compensation winding, find out the fault point and be fixed.

2. The operating speed is too low or uneven

1) There is a short circuit fault in the armature winding.

Check and measure to find out the short circuit point of the armature winding, repair or replace the armature winding.

2) There is a short circuit fault between the commutator pieces of the armature.

Check the condition of the entire commutator segment, carefully clean the residues such as solder, copper shavings, burrs, and other residues between the commutator segments, and eliminate potential short-circuit fault points.

3) The brush position is incorrect.

Adjust brush position.

4) The polarity of the stator commutation pole winding is wrongly connected, and long yellow sparks appear on the commutator.

Check and confirm that the polarity of the commutation pole winding is wrongly connected, and then correct the wiring.

5) The power supply voltage is too low.

Adjust the power supply voltage so that it reaches the rated value.

3. The speed is too high and accompanied by violent sparks

1) Excessive resistance of excitation winding or open circuit.

Use the resistance file of the multimeter to carefully check whether all the terminals in the excitation winding circuit have poor contact caused by the oxide layer so that the resistance of the excitation circuit can recover and reach the normal resistance value.

2) Turn-to-turn short circuit of excitation winding.

Check and measure to confirm the short-circuit fault range, and repair or replace the excitation winding as the case may be.

3) The polarity of the shunt excitation winding is wrongly connected.

Find and confirm that the polarity wiring of the shunt winding is wrong, and re-wiring according to the correct method.

4) There is a short circuit or open circuit fault in the armature winding.

Check and measure the short circuit or open circuit point, and repair or replace the armature winding as the case may be.

5) The load of the series excitation motor is too light.

After inspection, the load of the series-excited motor is indeed too light, and the load should be increased appropriately to facilitate the safety of starting.

6) The polarity of the series winding of the compound excitation motor is wrongly connected.

Carefully check the wiring of the series winding, find out the error, and re-wire according to the correct method.

7) The brush is offset from the original normal position.

After inspection, if it is indeed a brush position offset fault, the brushes can be reconfigured according to the original mark, or the correct position of the brushes can be found again by induction method, and the brushes can be reconfigured.

4. The armature overheats during operation

1) The motor is overloaded or started frequently beyond the specification.

Reduce load or reduce frequent starts.

2) There is a short circuit or ground fault in the armature winding.

Check and measure to confirm the exact position of the winding short circuit or grounding, and repair or replace the armature winding as the case may be.

3) There is an inter-chip short circuit in the commutator.

Remove solder, copper shavings and burrs between the commutator segments.

4) Too much brush spring pressure makes the commutator abnormally hot.

Adjust brush spring pressure.

5) The armature rubs against the stator poles.

Check whether the large and small end caps and pole cores of the motor are loose or not tightened properly, find out the fault and repair it.

6) The air gap of the main magnetic pole of the stator is uneven.

Check the main poles of the stator and adjust them thoroughly.

7) The cooling condition of the motor is deteriorating.

Clean the dust filter and air duct, and check whether the fan is defective.

8) The power supply voltage of the shunt excitation and compound excitation motor is too low.

Measure the power supply voltage with a voltmeter, find out the cause of the low voltage, and restore it to the rated value.