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Crane failure and troubleshooting (electrical equipment part)

Update time : 2020-09-12 Publisher:Dotrum

AC motor failure and cause status:

1. The entire motor overheats evenly
The cause of the failure: (1) The electric connection rate (JC%) increased, causing overload (2) Working under low voltage (3) Improper motor selection (4) The crane performance parameters were changed after maintenance
Remedy: (1) Reduce the heavy load of the crane or replace the motor corresponding to JC% (2) If the voltage is lower than 10% of the rated voltage, stop working (3) Choose a suitable motor (4) Maintain the crane design parameters
 
2. Local overheating of stator
Cause of failure: partial short circuit between the stator silicon steel sheets
Remedy: Eliminate the cause of the short circuit and wipe the repaired place with insulating paint
 
3. Local overheating of stator winding
The cause of the failure: (1) ΔY wiring error. (2) Two places in a phase winding are short-circuited with the shell
Remedy: (1) Check and eliminate wiring errors (2) Repair a phase winding
 
4. The temperature of the rotor rises, the stator has a large current impact, and the motor cannot reach full speed under rated load
Reasons for failure: (1) Poor contact between winding ends, neutral points or parallel windings. (2) Poor contact between winding and slip ring. (3) There is poor contact in the brush equipment. (4) There is poor contact in the rotor circuit.
Remedy: (1) Check the welds and eliminate defects. (2) Check the connection status. (3) Check and adjust the brush equipment (4) Check the looseness and poor contact and repair; check the resistance and replace the broken.
 
5. The motor vibrates when working
The cause of the failure: (1) The motor shaft and the reducer shaft are concentric. (2) Bearing damage and wear. (3) The rotor is deformed.
Remedy: (1) re-install the line (2) replace the bearing (3) repair the AC motor
 
6. The motor makes an abnormal sound when it is working
Causes of failure: (1) Stator phase shift (2) Stator core is not compressed (3) Bearing wear (4) Slot wedges expansion.
Remedy: (1) Check the wiring and correct it (2) Check and repair the stator (3) Replace the bearing (4) Saw off the swollen wedge or replace it.
 
7. The speed of the motor slows down after being loaded
The cause of the fault: (1) Short circuit at the end of the rotor (2) Two groundings in the rotor winding
Remedy: (1) Check and eliminate the short-circuit phenomenon (2) Check each turn of the coil, repair the road and eliminate the short-circuit
 
8. Friction between stator and rotor when the motor is running
Causes of failure: (1) Bearing wear, bearing end cover incorrect, stator or rotor core deformed (2) Incorrect connection of stator winding coils, resulting in unbalanced magnetic flux
Remedy: (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 determine that the current in each phase should be equal
 
9. Sparks on the brush or scorched slip ring when the motor is working
Causes of failure: (1) The brush is not well polished (2) The brush is too loose in the brush holder (3) The brush and slip ring are dirty (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
Remedy: (1) Grind the brush (2) Adjust the brush or grind properly (3) Wipe the slip ring clean with alcohol (4) Turn and grind the smooth ring (5) Adjust the brush pressure (18~20kPa) ( 6) Replace (7) Check the feeder and brushes of the brush holder, and correct them
 
10. Open slip ring
Cause of failure: dirty slip ring and brush equipment
Elimination method: clean dirt and descaling
 
 
AC electromagnet failure and cause status:
1. The coil is overheated
Reasons for failure: (1) Electromagnet suction is overloaded (2) There is a gap between the fixed part and the movable part of the magnetic current path (3) The coil voltage does not match the grid voltage
Remedy: (1) Adjust the spring tension (2) Eliminate the intermittent (3) Replace the coil or change the connection method
 
2. Louder at work
Reasons for failure: (1) Electromagnet overload (2) Dirt on the working surface of the magnetic flow path (3) Deflection of the magnetic system
Remedy: (1) Adjust the spring (2) Eliminate dirt (3) Adjust the mechanical part of the brake to eliminate deflection
 
3. Cannot overcome the spring force
Causes of failure: (1) Electromagnet overload (2) The main spring force is too large (3) The voltage in the power grid is low
Remedy: (1) (2) Adjust the main spring force of the brake (3) Suspend work
 
AC contactor and relay failure and cause status:
1. Coil heating
The cause of the failure: (1) Coil overload (2) The movement of the magnetic current path cannot touch the fixed part
Remedy: (1) Reduce the pressure of the movable contact on the fixed contact (2) Eliminate deflection, jams, dirt, or replace the coil
2. Increased buzzing of contactors
The cause of the failure: (1) Coil overload (2) Dirt on the surface of the magnetic flow path (3) Jam phenomenon in the automatic adjustment system of the magnetic path.
Elimination methods: (1) Reduce the contact pressure (2) Eliminate dirt (3) Eliminate jams
3. Touch hair hot or burned (damaged)
Reasons for failure: (1) Insufficient contact pressure (2) Dirty contacts
Remedy: (1) Adjust the pressure (2) Remove or replace
4. The main contactor cannot be connected
The cause of the failure: (1) The knife switch is not closed, the emergency switch is not closed (2) The warehouse switch is not turned on (3) The controller handle is not returned to the zero position (4) The control circuit fuse is blown (5) Line No electricity
Remedy: (1) (2) Close the switch (3) Return the handle to zero (4) Check or replace the fuse (5) Check whether the circuit has voltage
 
Cranes frequently trip during operation
Causes of failure: (1) Insufficient contact pressure (2) Contact burning (3) Dirty contacts (4) Overload operation, resulting in excessive current (5) The sliding contact lines are parallel, and the current collector and the sliding lines are in poor contact
Remedy: (1) Adjust the contact pressure (2) Replace the contact or polish and repair (3) Clean (4) Reduce the load (5) Trim the track or trench sliding contact line
 
 
Hydraulic electromagnet failure and cause status:
1. The push rod does not move after power on
The cause of the fault: (1) The push rod is stuck (2) The network voltage is lower than 85% of the rated voltage (3) The delay relay (on the ZLO silicon rectifier) ​​is too short (4) The rectifier device does not work (5) The rectifier device Damaged (6) The normally open contact of the time relay does not work (7) No oil or serious oil leakage
Remedy: (1) Eliminate jams (2) Increase the voltage (3) Adjust the delay relay, t delay ≈0.5s (4) Repair or replace (5) Repair or replace (6) Repair contacts (7) Repair seal Device, refueling
 
2. Small push rod stroke
Causes of failure: (1) Insufficient oil (2) There is gas between the piston and the bearing (3) The stroke is too small
Elimination method: (1) Replenishing oil volume (2) Exhaust gas (3) Adjust appropriately
 
3. After the electromagnet works, the stroke is gradually reduced
Causes of failure: (1) Oil leakage from the cylinder (2) The toothed valve and the moving iron core valve are not tightly sealed (3) The sealing ring is seriously damaged
Remedy: (1) Replace the oil cylinder (2) Remove the mechanical impurities on the valve plate (3) Replace the sealing ring
 
4. Starting time is too long
The cause of the fault: (1) The voltage is too low (2) The moving part is stuck (3) The brake braking torque is too large
Remedy: (1) Increase the voltage (2) Remove the stuck fault (3) Adjust the braking torque to the rated value
 
5. Braking time is too long
Reasons for failure: (1) Time relay contacts cannot be opened (2) The moving part is stuck (3) The oil circuit is blocked (4) The mechanical part is faulty
Remedy: (1) Check and repair the contacts (2) Remove jams (3) Dredge the oil circuit (4) Eliminate mechanical failures
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