Common faults and treatment methods of asynchronous motors

1. The power is not connected: check the switch, melted wire, each pair of contacts and the motor lead wire.

2. Winding open circuit: heat the open circuit to the temperature allowed by the insulation level. Soften the paint, then pick up the broken wire, repair the broken part with the same specification wire, wrap the insulation, and then paint and bake Dry treatment.

3. Winding grounding or short-circuit between phases and turns: The treatment method is the same as above, except that the grounded or short-circuited parts are well insulated, and then painted and dried.

4. Winding wiring error: check the wiring diagram, heat the end and reconnect it according to the correct connection method (including binding, insulation treatment and painting)

5. Melt blown: find out the cause, eliminate the fault, and prepare a new melt according to the motor specifications.

6. Misoperation of winding rotor motor starting: check the position of the collector ring short-circuit device and the starting varistor. When starting, the varistor should be connected in series with 0 first, and then the short-circuit device should be connected after starting.

7. The setting value of the overcurrent relay is too small: increase it appropriately.

8. The oil cup of the old start switch is short of oil: add new oil to reach the oil level.

9. Control equipment wiring error: correct the wiring.

After the motor is connected to the power supply, the melting wire is burned out

1. Single-phase start: check the power cord, motor lead wire, fuse, switch contact, find out the broken wire or false connection fault and repair it.

2. The stator and rotor windings are grounded or short-circuited: correct the error.

3. The motor load is too large or jammed: adjust the load to the rated value and eliminate the failure of the dragged mechanism.

4. The cross-sectional area of the melt is too small: the melt does not protect the motor from overloading. Generally, the melt should be selected according to the following formula, and the rated current of the melt = locked-rotor current/2~3.

5. The starting resistance of the wound rotor motor is too small or short-circuited: Eliminate the short-circuit fault or increase the starting resistance.

6. Short circuit between the power supply and the motor: check the short-circuit point and repair it.

After the motor is energized, the motor does not start, buzzing

1. Improper selection of slot coordination after changing pole rewinding: select reasonable winding form and winding pitch; appropriate small rotor diameter; recalculate winding parameters.

2. The stator and rotor windings are short-circuited: find out the breaking point for repair; check the contact state of the winding rotor brush and the slip ring, and check whether the starting resistance is open or the resistance is too large.

3. The winding lead wires are short-circuited all the time or the windings are connected reversely: Direct current is connected to the stator winding, and check the winding polarity (using a compass) to determine whether the winding head and end are correct.

4. The motor load is too large or stuck: check the equipment and troubleshoot.

5. The power fails to be fully connected: replace the fused melt; tighten the loose screw of the terminal; use a multimeter to check the power cord for disconnection or false connection failure, and then repair it.

6. The voltage is too low: If the delta connection motor is mistakenly connected to a Y connection, change it back to the delta connection; if the power supply voltage is too low, contact the power supply department to solve it; if the voltage drop on the power line is too large and the voltage is too low, change the thicker cable line.

7. For small motors, the grease becomes hard or the assembly is too tight: select the appropriate grease to improve the assembly quality.

Electric motor housing

1. The power line and the ground line are wrong: correct the error.

2. The motor winding is damp and the insulation is seriously aging: the motor is dried; the aging insulation needs to be updated.

3. Lead wire and junction box ground: wrap or update lead wire insulation; repair junction box.

4. The coil end touches the end cover to ground: remove the end cover, check the grounding point, the coil grounding point should be wrapped, insulated and painted, and the inner wall of the end cover should be padded with insulating paper.

The ammeter pointer is unstable and swings when the motor is unloaded or loaded

1. The one-phase brush of the wound rotor motor has poor contact: adjust the brush pressure and improve the contact surface between the brush and the collector ring.

2. Poor contact of the short-circuit device of the collector ring of the wound rotor motor: repair or update the short-circuit device.

3. Open welding or broken bars of cage rotor: use transformer or other methods to check.

4. One-phase open circuit of the wound rotor: check the open circuit with a calibration lamp, multimeter, etc. to remove the fault.

The motor is difficult to start. After the rated load is added, the motor speed is lower than the rated speed

1. The power supply voltage is too low: use a voltmeter or a multimeter to check the power supply voltage at the input end of the motor, and then deal with it.

2. Wrong connection of △ connection winding into Y connection: change Y connection back to △ connection.

3. Unwelded or broken cage rotor: repair after checking for unwelded or broken.

4. Poor contact between the wire-wound rotor brush or the starting varistor: check the contact part of the brush and the starting varistor

5. The stator and rotor windings have local coils connected incorrectly or reversed: see serial number 1 in this table.

6. Too many turns during rewinding: Rewind according to the correct number of turns.

7. One-phase open circuit of the wound rotor: Check the open circuit with a check lamp multimeter, etc., and then eliminate the fault.

8. Poor contact between the brush and the slip ring: improve the contact area between the brush and the slip ring, such as grinding the contact surface of the brush, the voltage regulating brush, the surface of the rotating slip ring, etc.

Low insulation resistance

1. The winding is damp or wet: heat and dry it.

2. Winding insulation is covered with dust and grease: clean the winding grease, and dry and immerse it.

3. The motor terminal board is damaged and the lead wire insulation is aging. Broken: repack the lead wire insulation, replace or repair the lead box and junction box.

4. Winding insulation aging: it can continue to be used after identification, it can be cleaned, dried, and repainted. If the insulation is aging and cannot operate safely, the insulation needs to be replaced.

The three-phase no-load current is symmetrical and balanced, but generally increases

1. The number of turns of the coil is insufficient when rewinding: rewind the coil and increase the number of reasonable turns.

2. Y is connected to the motor, and the wrong connection is △ connection: change the winding connection to Y connection.

3. The power supply voltage is too high: measure the power supply voltage, if the power supply itself is too high, negotiate with the power supply department to solve it.

4. Improper assembly of the motor (such as reverse installation, unaligned stator and rotor cores, uneven fixing of the end cover bolts, which makes the end cover skewed or loose): Check the assembly quality and eliminate the fault.

5. Uneven or enlarged air gap: Adjust the air gap. For the motor that has used the rotor, it is necessary to replace the rotor or change the winding to correct the problem of large no-load current.

6. When the wire is removed, the iron core is overheated and burned: repair the iron core or recalculate the winding to compensate.

There is abnormal noise when the motor is running

1. Improper slot matching when changing pole rewinding: check the stator and rotor slot matching.

2. Rotor wipes insulating paper or slot wedges: cut the insulating paper or repair the slot wedges.

3. The bearing is worn or faulty: repair or replace the new bearing.

4. The stator and rotor cores are loose: check the cause of vibration, and re-compact the cores.

5. The voltage is too high or the three-phase voltage is unbalanced: measure the power supply voltage, check the over-voltage and the unbalanced cause and deal with it.

6. Wrong connection of stator winding: see serial number 1 in this table.

7. The winding is faulty (such as short circuit): see serial number 1 in this table.

8. When rewinding, the number of turns of each phase is not equal: rewind the wire and correct the number of turns.

9. Bearing lack of grease: clean the bearing and fill it with grease so that it fills 1/2 to 1/3 of the net volume of the bearing chamber.

10. The fan hits the air hood or the air duct is blocked: repair the fan and air hood to make their geometric dimensions correct, and clean the air duct.

11. The breath is uneven and the stator and rotor rub together.

The motor overheats or smokes

1. The power supply voltage is too high, so that the core magnetic flux density is oversaturated and the motor temperature rises too high: If the power supply voltage exceeds the standard by a lot, contact the power supply department to solve it.

2. The power supply voltage is too low, and the motor temperature rises too high under the rated load: if the power line voltage drop is too large, you can replace the thicker power line; if the power supply voltage is too low, you can contact the power supply department to improve voltage.

3. When the wire is burnt, the iron core is burned, which increases the iron loss: do the iron core inspection test, repair the iron core, and troubleshoot.

4. The stator and rotor cores rub against each other: Check the cause of the failure. If the bearing clearance exceeds the limit, replace the new bearing. If the shaft is bent, investigate and deal with it. If the core is loose or deformed, the core should be dealt with to eliminate the fault.

5. The winding surface is covered with dirt or foreign matter, which affects the heat dissipation of the motor: sweep or clean the motor, and make the motor ventilation channel unblocked.

6. The motor is overloaded or the resistance of the production machinery of the drag is too large, causing the motor to heat up: eliminate the failure of the dragging machinery, reduce the resistance, according to the current indication, if the rated current is exceeded, reduce the load, replace the larger capacity motor or take measures to increase the capacity .

7. The motor frequently starts or the number of forward and reverse rotations is too much: reduce the number of motor starting and forward and reverse rotations or replace with a suitable motor.

8. The cage rotor bar is broken or the winding of the wound rotor winding is loose, and the motor generates heat under the rated load, which causes the motor temperature to rise too high: find out the broken bar and loose parts, re-welding or tighten the fixing screws.

9. Short-circuit between winding turns and short-circuit between windings and grounding of windings: According to the number 1 of this table.

10. The inlet air temperature is too high: check whether the cooling system device is faulty, and check whether the ambient temperature is normal.

11. Fan failure, poor ventilation: Check whether the motor fan is damaged, whether the fan blade is deformed or not fixed. Replace the fan if necessary.

12. Motor two-phase operation: check the melting wire, switch contact point, and troubleshoot.

13. Poor winding impregnation after rewinding: a secondary impregnation process is required, preferably vacuum impregnation.

14. The ambient temperature increases or the motor ventilation duct is blocked: improve the ambient temperature, take cooling measures, isolate the high temperature heat source near the motor, and avoid the motor from being exposed to sunlight.

15. Winding wiring error: Y-connection motor is wrongly connected to △-connection, or △-connection motor is wrongly connected to Y-connection, the connection should be corrected.

The no-load current is unbalanced when the motor is running at no load, and the difference is very large

1. When rewinding, the number of turns of the three-phase winding is uneven: the winding is rewinded and corrected.

2. Wrong connection of the winding head and tail ends: find out the head and tail ends, and start the motor test after correction.

3. Unbalanced power supply voltage: measure the power supply voltage, find out the cause, and eliminate it.

4. The winding is faulty, such as short circuit between turns, reverse connection of a certain group of coils, etc.: Disassemble the motor to check the winding polarity and fault, and then correct or eliminate the fault.

Interlayer insulation breakdown

1. The mat material between layers is poor, or the thickness is not enough: use a good material, such as epoxy glass cloth mat mat, or thicken the mat appropriately.

2. The pads between the layers are offset or the size is inappropriate: the blanking size is required to be correct, the operation is careful, and the process is strictly followed.

3. The loose coil makes the interlayer mat strips wear: groove lining or thick mat strips can be added; or the VPI "whole dip" process can be adopted.

Turn-to-turn insulation breakdown

1. Poor inter-turn insulation material: Reinforce with resin varnish or use "three-in-one" powder mica tape.

2. Winding. Inter-turn insulation is damaged during wire embedding: strictly follow the process regulations.

3. Insufficient insulation thickness between turns or unreasonable structure: According to the voltage between turns (see Chapter 3), choose the right insulation thickness or insulation structure between turns.

Winding ground fault

1. The motor is overloaded for a long time, and the insulation aging and deterioration cause insulation to ground breakdown: adjust the load or replace the motor with suitable capacity to avoid local overheating.

2. Transmission line lightning overvoltage or operating overvoltage breakdown insulation: add or check lightning protection devices.

3. Due to the accumulation of conductive dust, the creepage distance is reduced and the ground breakdown or flashover occurs: clean the insulation regularly, and add a dust-proof sealed insulation device.

4. After the ventilation duct gasket, the tooth pressure piece is welded, the iron core is not tightly laminated, the tooth part vibrates and the bent tooth pressure piece scratches the coil insulation, resulting in winding ground fault. : Inspect the welding quality and deformation of each part in detail, and make sure that the gaskets and tooth pressing pieces are well fixed after correction or repair welding. When the iron core is not tightly laminated, add silicon steel sheet or increase the tooth bead, and re-press the iron core (for the built-in pressed iron core, the iron core does not need to be taken out of the machine base).

5. Due to the short-circuit and scorched insulation of the coil, the ground fault is caused: check the cause of the short-circuit, remove part of the coil, add insulation and immerse and bake it.

Winding open

1. The end of the coil is subjected to mechanical and electromagnetic forces, which leads to the opening of the wire welding point: check the welding point, re-weld and strengthen the fixing measures of the winding end.

2. Improper welding process, overheating of the welding point causes open welding: strictly follow the welding process.

3. The wire material is not good, and there are defects such as interlayer peeling: replace qualified wires and conduct insulation treatment.

Winding short circuit

1. Line overvoltage: adjust the overvoltage protection value.

2. Winding insulation aging: replace the insulation of the winding or related parts.

3. Excessive dust accumulation in the winding insulation gap: sweep or wash the insulation, and then dry-dip-dry.

4. The insulation is damaged after being subjected to mechanical force and electromagnetic force: local reinforcement or replacement of windings and insulation, and then immersion and baking.

Stator coil insulation wear or electric corrosion

1. The gap between the coil and the slot ratio is too large (for the molded winding using the "molding" process): 1032 paint or resin paint can be impregnated to fill the gap in the slot.

2. The slot wedge is loose: replace the slot wedge (adjust the width or height of the slot wedge) or add a pad under the slot.

3. Outer size of coil: Rewind the coil according to the drawing requirements, see Chapters 2 and 3.

4. Failure of the anti-corona paint: take out the coil and repaint the anti-corona semiconductor paint.

5. The insulation is stuck with oily dirt: clean or blow the dirt on the winding.

Large leakage current

1. The motor is damp: dry the winding after cleaning.

2. There is oil stain on the insulating surface. Dust: sweep or wash the winding insulation.

3. Insulation aging: replace the insulation.

Increased dielectric loss angle

1. The coil is damaged, causing more air gaps inside the insulation: take vacuum impregnation treatment.

2. Insulation damage: Reinforce locally after cleaning, then dip paint and dry.

3. Improper insulation treatment: Improve insulation treatment methods.

4. Insulation aging: replace the insulation.

Wear and breakdown between coil and end ferrule

1. Loose coil: After binding, dipping resin paint, and then drying.

2. The end band is not firmly fixed: the same as Article 20 in Chapter 20.

3. The insulation is full of dust: clean the insulation. If the wire is re-inserted, the material of the end band can be changed to non-metallic.

Mechanical damage to the coil end insulation

1. Bumps during disassembly and assembly: Due to the operation according to the process regulations, the local damage can be repaired with epoxy glue.

2. Bump the nearby coil when repairing or replacing the coil locally: Check the fault condition, and you can repair or replace part of the coil locally.

Loose wedge

1. The material of the slot wedge is aging and shrinking: changing the slot wedge, the 3240 epoxy glass cloth board used in F and B insulation in China has stable physical and chemical properties and good thermal stability.

2. The mat under the wedge is aging and loose: the thickened mat is re-inserted into the mat and groove wedge.

3. Improper fit between slot wedge size and core: Refer to Chapter 3 to select slot wedge size.

4. The whole magnetic trough wedge is worn under the action of electromagnetic force: switch to magnetic trough mud; if the whole magnetic trough mud is used, the VPI "whole immersion" process should be adopted.

The cage bars protruding from the core are arched

1. When the motor is in the state of starting, braking and forward and reverse rotation, a large current flows in the cage bar, which causes the cage bar to locally expand under the electric heating effect. When the start and braking state ends, the cage bar begins to contract, and the centrifugal force Under the action, when the end of the cage bar is not strong enough, the cage bar arching failure occurs:

1. Heat the arched part and straighten the arched part mechanically.

2. Remove the cage bar, straighten it and then insert it into the slot for welding.

3. Replace the cage bars with higher strength.

The end cage is bent in the direction of the rotor

1. This kind of failure often occurs on the rotor of a motor with a large circumferential speed and a solid end ring, which is not properly fixed by the steel end hoop. The cage bar has a circumferential inertia force on the end hoop.

Caused by:

2. Change the end hoop to a weft-free strap or replace the end hoop made of fiberglass.

3. Strengthen the fit between the end ring and the rotor bracket, and select a reasonable tolerance size.

Welded copper end ring, disconnected at the weld junction

1. To save copper material. When repairing, sometimes several pieces of copper material are welded to form a round end ring. If the welded end ring is poor, it will expand during operation and cut the stator insulation:

1. The integral end ring is forged with copper material.

2. Improve the welding process.

3. Cut the welding groove correctly.

The cast aluminum rotor blades are deformed or broken

1. Mechanical damage during disassembly and assembly: operate correctly according to process requirements.

2. The fan blade has inclusions when casting aluminum: use argon arc welding machine to repair welding.

3. Correct the deformed blades.

Broken cast aluminum rotor cage

1. The molten aluminum or the tank contains many impurities: check the chemical composition of the molten aluminum.

2. Old aluminum melted by fire is reused and contains impurities: old aluminum melted by fire cannot be reused directly.

3. In the case of single punching, the individual slots of the rotor blades are leaked: After the aluminum is melted, the leaking slots are punched.

4. The rotor core is pressed too tightly, the rotor core is expanded after aluminum casting, and the aluminum bar is broken due to excessive tension: replace the copper cage welding structure.

5. The pouring pauses in the middle, and the successively injected molten aluminum is not well combined: replace with a new rotor.

6. Early demoulding after aluminum casting: replace with a new rotor.

Cast aluminum rotor slot oblique lines are staggered and crooked

1. The groove wall is not neat when the rotor is laminated: melt the aluminum and re-laminate.

2. The false shaft oblique key and the keyway of the punching sheet are too loose: replace or repair the keyway.

3. After the rotor core is preheated, it is thrown around and the punching piece produces circumferential displacement: operate according to the process regulations.

4. The iron core stack pressure is small or has burrs: After melting the aluminum, re-press the iron and replace the copper cage welding structure.

The cage bars are loose in the trough

1. The size of the cage bar is too small: select the cage bar size according to the groove shape.

2. The groove size is inconsistent: correct the groove shape.

3. Cage bar or groove shape wear: correct the groove shape and replace the cage bar.

The wedge-shaped cage bars protrude from the notches

1. The motor speed is too high: check the rotor strength when changing the pole.

2. The current density of the cage is too large and the starting operation is unreasonable: the operation should be carried out according to the regulations.

Double-cage rotor copper strip welding

1. The motor starts and brakes under frequent heavy loads: the number of starts is performed according to the product manual.

2. When the end ring adopts the welding structure, the process is improper: the welding is performed correctly according to the process specification.

The copper cage breaks at the end ring

1. Produce mechanical vibration and loose cage bars in the groove: solve the vibration and loosening causes and failures.

2. When the end ring adopts a welding structure, the process is improper: the welding is performed correctly according to the process specification.

Copper cage welding

1. Improper welding process: follow the correct process for construction.

2. The gap between the cage bar and the end ring is not correct: make the gap uniform, between 0.1 and 0.12mm.

3. The cage bar is loose in the groove: deal with the looseness (see the previous method).

4. Unit vibration: solve the unit vibration.

5. Inappropriate electrode grades: select appropriate electrode grades.

6. Motor overload: Solve the problem of motor overload.

The aluminum end ring has axial and radial cracks

1. The molten aluminum contains slag during casting: control the pouring temperature and chemical composition.

2. Liquid aluminum contains impurities: remove impurities in liquid aluminum.

3. Unreasonable mold design: modify the design.

Motor vibration

1. Bearing wear: check the bearing clearance.

2. Uneven breath: adjust the air gap to meet the requirements.

3. Rotor imbalance: Check the cause, after cleaning, and after tightening the bolts, adjust the dynamic balance.

4. Insufficient cabinet strength: find the weak points for reinforcement and increase the mechanical strength.

5. Insufficient foundation strength or uneven installation: Reinforce the foundation, level and level the motor foot, and finally tighten it.

6. Fan unbalance: check and repair the fan, correct the geometry and balance.

7. The winding of the wound rotor is short-circuited

8. Open welding and open circuit of cage rotor: repair welding or replace cage bars

9. Stator winding failure (open circuit, short circuit, grounding, wrong connection, etc.)

10. Bending shaft: straighten the shaft.

11. The core is deformed or loose: correct the core, and then re-stack the core.

12. The installation of the backrest wheel or pulley does not meet the requirements: re-align, if necessary, check the backrest wheel or pulley and reinstall it.

13. The gear receiver is loose: check the gear receiver, make repairs, and follow the requirements.

14. Motor anchor bolts are loose: tighten the motor anchor bolts, or replace the unqualified anchor bolts.

Bearing heating exceeds the limit

1. Too much or too little grease: add grease according to the empirical formula given in this chapter

2. The oil is of poor quality and contains impurities: check for impurities in the oil, and replace clean grease.

3. The bearing inner and outer cover are too tight: when it is too loose, use agricultural machinery 2# adhesive or low-temperature iron-plating treatment. When it is too tight, the shaft journal should be adjusted appropriately to meet the tolerance requirements.

4. The oil seal is too tight: replace or repair the oil seal.

5. The bearing cover is eccentric and rubs against the shaft: repair the bearing inner cover to make the clearance with the shaft suitable.

6. The end caps or bearing caps on both sides of the motor are not installed flat: Install the end caps or bearing caps into the stopper according to the correct process, and then tighten the screws evenly.

7. Bearing failure, wear, debris, etc.: replace the damaged bearing, thoroughly clean the bearing containing impurities, and change the oil.

8. The motor and transmission mechanism are eccentric or the transmission belt is too tight: calibrate the center line of the connection between the motor and the transmission mechanism, and adjust the tension of the transmission belt:.

9. Select the bearing model to be small and overloaded, so that the rolling elements can bear excessive load: select the appropriate bearing model.

10. The bearing clearance is too large or too small: replace with a new bearing.

11. Sliding bearing oil ring rotation is not flexible: check and repair the oil ring to make the oil ring size correct and correct the balance.