Three phase asynchronous motors common faults and treatment methods
Three phase asynchronous motor faults are usually divided into mechanical faults and electrical faults. Electrical faults include short circuit and open circuit of stator and rotor windings, brush and starting equipment faults, etc. Mechanical faults include excessive vibration, bearing overheating, stator and rotor friction and abnormal noise.
In order to ensure normal operation, the motor should be maintained correctly and regularly. An ammeter should be installed to monitor the load current and an overcurrent protection device should be provided for the motor with higher power. During the operation of the motor, the change of its supply voltage and frequency should be observed. Otherwise, the motor may overheat or run abnormally.
Common motor stator winding damage status and reasons are analyzed as follows:
(1) The ground-to-ground breakdown of windings is usually in the stator notch or the bottom of the groove. After the ground-to-ground breakdown, the spark burns the paint skin of the wire and causes the inter-turn breakdown. If this happens to new motors or motors that have not been used for a long time, it should mostly belong to manufacturing quality problems.
(2) The inter-turn breakdown of winding is mostly found in the end of the stator winding, and there are often several local wires burned off. There may be two reasons for the inter-turn breakdown and damage of winding: one is the quality problem of enameled wire; The other is that the paint skin of the wire is scratched when the wire is embedded or the paint skin of the wire is damaged during the handling of the workpiece.
(3) The damage caused by the burning of the one-phase or two-phase winding is likely to be caused by the lack of phase operation, which is generally caused by the improper use of the user.
Common fault judgment and treatment methods of three phase asynchronous motor are shown in the following table.
Symptom 1
The motor does not start or has a low speed after being energized
Cause analysis:
1. The power supply voltage is too low
2. Fuse melt is broken, and the power supply is out of phase
3. The STATOR winding or external circuit has a phase break, winding rotor internal or external break, poor contact
4. The motor is incorrectly connected
5. The motor is overloaded or stuck mechanically
6. Broken bar or unwelded cage rotor
Processing method:
1. Checking the Power Supply
2. Check the cause, rectify the fault, and replace the fuse
3. Use megohm meter or multimeter to check whether there is a break or poor contact, after finding out the break, deal with the poor contact
4. Correct the wiring mode
5. Adjust the load and handle the mechanical parts
6. Replace or repair the copper strip, or replace the cast aluminum rotor
Symptom 2
Motor overheating or internal smoke fire
Cause analysis:
1 Motor overload
2 The power supply voltage is too high
3. The ambient temperature is too high. Ventilation and heat dissipation obstacle
4. Stator winding short circuit or ground
5. Missing phase operation
6. The motor is damp or not thoroughly dried after repair
7. Rotor friction
8. The motor connection is wrong
9. Boot too frequently
Processing method:
1. Reduce load or replace large-capacity motor
2. Check and adjust the power supply voltage
3. Replace the B or F class insulation motor. Lower the ambient temperature. Improve ventilation conditions
4. Check winding current resistance and insulation resistance. Dealing with short circuit
5. Check THE power supply and motor WINdings respectively, find out the fault points and repair them
6. If the heat is not serious, insulation is good, should be thoroughly dried
7. Measure the air gap, check bearing wear, find out the cause and repair
8. Change to correct connection method
9. Start at the specified frequency
Symptom 3
Brush sparks too large, slip ring overheating
Cause analysis:
1. The brush spark is too large
2. Internal overheating
3. Dirt and sundries on the surface of the slip ring
4. The slip ring is uneven. The brush is not in strict contact with the slip ring
5. The brush brand does not match. Wrong size
6. The brush pressure is too high or too low
Processing method:
1. Adjust and repair brushes and slip rings
2. Eliminate the cause of overheating
3. Remove dirt and debris to make the surface contact with the brush well
4. Clean slip ring. Grind brush
5. Replace the appropriate brush
6. Adjust the brush pressure to the specified value
Symptom 4
The three-phase current is too large or unbalanced
Cause analysis:
1. A phase of the stator winding is incorrectly connected
2. The three-phase power supply voltage is unbalanced
3. Part of the stator winding is short-circuited
4. Single-phase operation
5. Stator winding is open circuit phenomenon
Processing method:
1. Re-identify the first and the second end before wiring operation
2. Checking Power Supplies
3. Find the short-circuit winding. Repair or replacement
4. Check all contact points of fuse and control device to eliminate accidents
5. Find the circuit winding. Repair or replacement
Symptom 5
Vibration is too large
Cause analysis:
1. The motor base is uneven
2. Bearing oil shortage, bending or damage
3. Local short circuit of stator or rotor winding
4. The rotating part is unbalanced. Loose joints
5. Stator and rotor rub against each other
Processing method:
1. Reinstall and level the machine base
2. Cleaning and refueling. Alignment or bearing replacement
3. Find the short circuit and repair it
4. Correct the balance. Find loose places and tighten the bolts
5. Check and correct the clearance of moving and static parts
