Causes and solutions of common failures of crane AC motors

The lifting motor is an important part of the crane operation and provides power for the operation and lifting of the crane. If there is a problem with the AC motor, it will seriously affect the normal operation of the equipment. The editor will introduce to you the common faults of the lifting motor, as well as the reasons and solutions for the faults.

1. The entire motor overheats evenly

reason:

(1) The connection rate (JC%) increases, causing overload

(2) Working under low voltage

(3) Improper selection of motor

(4) The crane performance parameters were changed after maintenance

Solution:

(1) Reduce the heavy degree of crane or replace the corresponding motor of JC%

(2) The voltage is lower than 10% of the rated voltage and stop working

(3) Choose a suitable motor

(4) Maintain and maintain crane design parameters

2. Local overheating of the stator

Cause of failure: Partial short circuit between the stator silicon steel sheets

Solution: Eliminate the cause of the short circuit and wipe the repaired place with insulating paint

3. Local overheating of stator winding

cause of issue:

(1) ΔY wiring error

(2) Two places in a phase winding are short-circuited with the shell

Solution:

(1) Check and eliminate wiring errors

(2) Repair a certain phase winding

4. The temperature of the rotor rises, the stator has a large current impact, and the motor cannot reach full speed under the rated load.

cause of issue:

(1) Poor contact between winding ends, neutral points or parallel windings

(2) Poor contact between winding and slip ring

(3) Poor contact in brush equipment

(4) Poor contact in the rotor circuit

Solution:

(1) Check the welds and eliminate defects

(2) Check the connection status

(3) Check and adjust electric brush equipment

(4) Check and repair the looseness and poor contact; check the resistance and replace the broken

5. The motor vibrates when working

cause of issue:

(1) The motor shaft and the shaft of the reducer are concentric

(2) Bearing damage and wear

(3) Deformation of the rotor

Solution:

(1) Re-install the line

(2) Replace the bearing

(3) Maintenance

6. The motor makes an abnormal sound when it is working

cause of issue:

(1) Stator phase shift

(2) The stator core is not compressed

(3) Bearing wear

(4) Groove wedge expansion

Solution:

(1) Check the wiring and correct it

(2) Check and repair the stator

(3) Replace the bearing

(4) Saw off the expanded wedge or replace it

7. The speed of the motor slows down after being loaded

cause of issue:

(1) Short circuit at the end of the rotor

(2) The rotor winding has two grounding points

Solution:

(1) Check and eliminate short-circuit phenomenon

(2) Check every turn of the coil, repair the road and eliminate the short circuit

8. Friction between stator and rotor when the motor is running

cause of issue:

(1) The bearing is worn, the bearing end cover is not correct, and the stator or rotor core is deformed

(2) The coils of the stator windings are not connected correctly, which makes the magnetic flux unbalanced

Solution:

(1) Replace the failed bearing; check the position of the end cover; remove the spurs on the stator or rotor core

(2) Check and make the coil wiring correct, and measure that the current in each phase should be equal

9. Sparks on the brush or scorched slip ring when the motor is working

cause of issue:

(1) The brush is not well polished

(2) The brush is too loose in the brush grip

(3) Dirty brushes and slip rings

(4) The slip ring is uneven, causing the brush to jump

(5) Insufficient brush pressure

(6) Wrong brush brand

(7) Uneven current distribution between brushes

Solution:

(1) Grind the brush

(2) Adjust the brush or grind properly

(3) Wipe the slip ring clean with alcohol

(4) Turning and grinding smooth ring

(5) Adjust the brush pressure (18～20kPa)

(6) Replace

(7) Check and correct the feeder and brushes of the brush holder

10. Open slip ring

Cause of failure: dirty slip ring and brush equipment

Solution: Clean dirt and descaling

After the lifting motor has a problem, it should be shut down for inspection in time, and the work should be carried out after troubleshooting.

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