Common AC induction motor fault analysis, diagnosis and treatment

[Abstract] AC induction motor Zuowei power important equipment in the enterprise, all kinds of faults occur frequently, sometimes failure is a variety of reasons exist, through a variety of motor fault analysis, diagnosis and treatment, and considering the solution of equipment variety of methods. to the fastest, most accurate judgments, the purpose of handling and maintenance equipment, and diagnostic and treatment equipment the workers fault for reference.

[Keywords:] motor failure, treatment,

Introduction
Electric power companies, the motor will be a direct result of abnormal mechanical equipment stops and safety equipment and personal effects, reduce the starting rate of the device, causing cuts and production. I for the common faults of AC motor analysis and diagnosis, and do the corresponding measures in a timely manner to judge and deal with equipment failures and pitfalls of the equipment safe and stable operation of a very important role.

First, the induction motor fault analysis, diagnosis and treatment
General induction motor failure and mechanical reasons for the electromagnetic two reasons. Common failure analysis, diagnosis and treatment are as follows:
1. Induction motor can not start:
1.1 The motor can not start, have been dragged machinery stuck fault and motor starting equipment, and other aspects of body failed reason:
Approach: when the motor is not starting trouble, you can use multimeter to measure three-phase voltage, if the voltage is too low, should seek to increase the voltage, may be caused by: �� power cord is too small, start-drop too thick wires should be replaced. �� connected as star delta wiring wiring fault, but also a heavy start, triangle connection should start. �� transmission voltage is too low, the voltage should be increased to achieve the required voltage level. If the three-phase voltage imbalance or phase loss, that failure occurred in starting the device. If the three-phase voltage balance, but the motor speed is slow and a strange sound, this may be the load is too heavy, dragging the machine jammed. You should disconnect the power, moving the motor drive shaft, if the flexibility to balance shaft to rotate, that is overloaded and can not be flexible if the balance shaft to rotate, that is a mechanical jamming. If the three-phase voltage is normal and the motor does not turn, there may be failure or jamming the motor body seriously, at this time should be torn off the motor and mechanical drag, respectively, and the drag plate machinery moving motor shaft, and a separate starter motor, you can know the fault lies, as the appropriate treatment.

1.1.1 When determining the starting equipment failure, to check the switches, contacts and the terminal contacts of the contact situation, check the thermal overload relay contacts open and close the work of the current situation and the adjusted value is reasonable, check the fuse melt-off control situation, the fusing of the melt after the analysis of the reasons the state should be based on the requirements of motor starting to re-select, if the starter equipment, internal wiring is wrong, it should be corrected in the correct wiring.

1.1.2 When the body identified as the motor fails, you should check the stator and rotor windings is grounded or bearing is damaged. Winding inter-turn short-circuit ground or in part, the motor, been able to start but will lead to melt fuse and stops and the serious short-circuit will soon be smoke when the motor windings.

Check winding grounding method is often used: assault with a trillion on the table to check the winding insulation resistance, if there is ground fault, the table indicates the value is zero trillion assault. Winding short circuit: the bridge is usually measured with the arms of the balance of direct resistance, for winding ground, turn to turn short-circuit the processing is usually re-wound windings.

1.1.3 Other reasons
As a result of damage to the motor shaft bearing channeling position, sink, and even the rotor and the stator friction stuck, replace bearings.

If no insulation in the winter, places less well motors, grease should be checked.

2, the squirrel-cage motor below the rated speed after starting
2.1 reduce the speed when the motor is running:
2.1.1 Power supply voltage, such as lower voltage, the motor starting torque decreases, speed decreases. If the check is the voltage is too low, should improve the power supply voltage. Motor wiring error, windings should be connected in delta connection and the wrong star The voltage drop will Shixiang.

2.1.2 rotor resistance, if the squirrel cage rotor bar fault or open welding, showed decreased speed and starting torque. Conductance open fracture and welding section, the first visual inspection can be also be checked by means of instrumentation. Visual inspection: is View squirrel cage there arc sliver burning marks, with or without fracture and small cracks, end-ring connection is good. With Instrument check: One way is to run the motor to see if the ammeter indicates the motor stator current. in the squirrel cage rotor lead solder bar or open fracture failure, ammeter pointer will swing back. ammeter for not installing the motor, the motor stator windings can be received after the ammeter in series 15-20% Ue (Ue for the rated voltage of the three-phase AC power supply , (three-phase auto voltage regulator, moving the motor drive shaft, with the rotor position is different from the stator current will change, the pointer suddenly break down at the guide bar or open solder Department.

2.2 If the inspection is to be a slight drag machine jammed, so do not switch to a flexible shaft, it will barely drag load caused by the motor speed decreased.

3-phase asynchronous motor running current unbalance
Three-phase current imbalance caused by the main motor:
3.1 Three-phase voltage imbalance. If the power supply voltage imbalance of three-phase current unbalance when the motor is running, you can check the power supply voltage, to deal with it.

3.2 Individual Winding. Will cause the impedance of each phase are equal, the effect of three phase voltage, making the three-phase current imbalance.

3.3 As a result of equipment failure caused by motor starting phase voltage imbalance. For re-winding of the motor windings, in addition to the above reasons, but also may be due to an error or part of the coil wire coil turns have caused the error. Wiring should be checked for errors corrected . with a double bridge measuring the DC resistance of each phase winding, if the resistance difference is too large, then the number of turns in error should be re-wound.

4, when the temperature is too high to run asynchronous motor
Rise in temperature when the motor is running. Can check the following aspects and treatment.

4.1 The rise in temperature caused by overload operation. If the rise in temperature is determined by the inspection machinery by a dragging operation of the belt too tight and not flexible shaft caused mechanical maintenance personnel in conjunction with the belt to relax properly, dismantling machinery and equipment, the flexible shaft and should be kept running at rated load conditions.

4.2 The rise in temperature caused by poor working conditions. At this point can take a simple arbor shade or blower, the fan blowing. At the same time clear the motor itself should pay attention to the oil and dust wind tunnel to improve the self-cooling conditions.

4.3 Motor Operation failure caused by excessive temperature rise. Motor windings inter-turn short circuit and earth exist, or damage due to bearing operation, will cause the local temperature rise is too high. Then open the motor, visual smell, it has burnt . hand to touch, compare the temperature, find the short circuit Department, separate short-circuit part. bearing damage can replace the bearings.

4.4 the squirrel cage rotor bar fault, open solder temperature rise caused by excessive treatment of the rotor in operation.

4.5 In addition, the motor temperature is too high also on the motor voltage is too high or too low.

4.6 re-wound motor, the winding parameters may also result when the motor is running hot in the trial. At this point measure the three-phase motor load current, if greater than the rated value, then the number of turns is not enough, should be increased.

4.7 Reversible frequent or excessive number of starts may also cause the motor temperature is too high, then should reduce the number of motor reversing and start, or switch to other types of motors.

5, bearing induction motor running hot
Bearing operation temperature is higher than the specified value, said 85 �� heat. Overheated bearings when the motor is running, usually due to poor lubrication, poor installation and other causes, when there is overheating, you can find out the reasons from the following areas and make the appropriate treatment.

5.1. Bearing lubrication is good. When a hot bearing, the first motor to be open at both ends of the bearing caps, visual inspection of the grease. Impurities penetrated dirty grease, or dry bearings, etc. can cause overheating, can be reasonably replacement of grease used.

5.2 rooms bearing grease should not be too much or too little. Greases should be 1/2-2/3 of the total bearing chamber volume is appropriate.

5.3 The installation must have the proper bearing tolerance with. Bearing radial clearance is too large too small, the jacket is too tight with loose bearings caused by overheating of the motor running cause.

5.4 In addition, the coupling of improper installation, the belt too tight, vibration, motor operation is possible when the bearing heating. Then the coupling should be adjusted so that the two axes in a straight line, without affecting the speed, where appropriate, Relax belts, motor vibration during operation should be eliminated.

6, asynchronous motor noise when running
Noise when the motor is running, usually due to starting equipment failure, poor motor assembly and bearing damage caused by other reasons.

6.1 The main contact starting equipment caused missing running bad, or the motor windings of a phase break, running a humming sound. Starting equipment failures can be handled. The latter, direct resistance with a multimeter or table to check the motor windings appropriate repair or re-wound windings.

6.2 motor assembly bad, there are two common situations. One end caps and the stator (or solid end cap bearing caps and tighten the screws around the uneven and non-uniform meshing around the Mouth of the assembly, resulting in end cap (or bearing cap installation errors, affecting the concentricity of the stator and rotor, and second bearings, the jacket and shaft, shaft and hole cover is too loose, resulting in phase stator core and rotor rub, the assembly should be reasonable.

6.3 ball bearing, roller, and isolation within the coat rack and metal flaking and other serious wear and tear, resulting in a loud motor running noise and vibration of metal impact sound, and you should replace the bearings. In addition, re-wound stator winding insulation paper after pruning phase with the rotor is not rubbing, loose coupling shaft deformation of staff may occur, or noise, in those circumstances should identify the reason for the symptomatic treatment.

7, asynchronous motor running excessive vibration
Excessive vibration when the motor is running, usually due to both electromagnetic and mechanical causes.

7.1 supply voltage asymmetry, multi-winding short circuit and open circuit winding of individual branches, or failed to exercise stringent stator core equipment, squirrel cage rotor bar or open fracture more welding and so on. These reasons can cause electromagnetic motor vibration when running. motor shaft bent into an oval or spindle shaft and the shaft attached to some moving parts on the imbalance of these mechanical reasons can also cause vibration when motor is running. Therefore, Vibration occurs when the motor too large, it can first check the impact of the motor drive components, and then torn off and the coupling to the motor idling to be checked.

If the motor idling vibration is not large, this may be due to mechanical drag the motor shaft with the center find a closed, it could be the motor and the drag caused by mechanical vibration between the vibration motor. Determine the cause of the vibration after in conjunction with mechanical maintenance personnel to re-check for mechanical defects for processing.

7.2 If the motor idling vibration is greater, because the motor itself. At this time should be cut off the power to determine the cause of vibration is due to mechanical or electromagnetic aspects of causes.

Cut off the power immediately after the elimination of vibration, that is the electromagnetic reasons, you should check whether the disconnected winding parallel branches, squirrel cage rotor bar is open or broken weld. Winding parallel branch has broken meter resistor values available analysis. winding disconnected parallel branch there, after decapitation should be carefully identified for the insulated weld and, if necessary, to re-wound windings.

Cut off the power if the vibration persists, note the reason for the machinery, such as: rotor or belt imbalance, bent shaft, bearing failure and so on. Rotor unbalance can be static balance or equilibrium calibration. Pulley imbalances usually is due to the eccentric shaft hole may be turning after the inlay, slightly bent shaft can be adjusted or turned in press after the 1-2mm inlay, shaft bending over large surface can be welded at the bend of the surfacing layer of uniform, then cylindrical rotor basis to find center, lathes, grinders processed to meet the requirements on the size. Furthermore, the motor of the base concrete cracking or anchor bolts, tighten the cover screws are not so excessive vibration will cause the motor to identify the reasons , you can deal with these issues.

8, the isolation switch is closed after the burning fuse
Isolation switch is closed the main cause of the malfunction after the burning fuse:
8.1 The connection between the connector and the stator windings are shorted. Disassemble the motor terminal head, check the wire insulation.

Ground or short circuit the stator windings 8.2 see (1. Can not start the motor stator windings described approach grounded or short-circuit check.

8.3 motor load is too large or a mechanical jam. Then check the stator current with the ammeter and the rotation of the rotor without stuck phenomenon, to reduce the load and eliminate failure.

8.4 Fuse selection is too small or virtual access, check the connections and insurance.

9, the motor load current is larger
Motor load current is too large can check the following aspects Failure:
9.1 supply voltage is too high. When the power supply voltage higher than the rated voltage, so that greatly increased the saturation of the motor, so exciting current increase, while the motor iron core saturation also increased iron loss. Check power supply voltage, if the voltage level is too high , the lower voltage level. motor itself, the larger the air gap, open the motor, using the card, wild card inside diameter measurement of the stator and rotor diameter.

9.2 stator winding turns are not around enough. Rewinding the stator windings to increase the number of turns.

9.3 Motor improper assembly. Hand turn the motor test, such as the rotor rotation is not flexible. Axial displacement of the rotor may be too much. Or the cover bolts did not balance on the tight, you can relax turn the screw again.

9.4 star stator windings should be connected to form a triangle wiring wrong. Check with the nameplate of stator wiring requirements.

10, case charged
The main chassis and handling charged
10.1 Lead insulation damage or junction box connectors to touch. Check the insulation sleeve after the sleeve or wrap insulation cloth.

10.2 long end collision case. Remove the rear cover is grounded to eliminate the phenomenon. At this point should be end of winding a layer of insulating paint brush, and pad of paper and then mounted on the insulating cover. Reposted elsewhere in the Research Papers Download http: / / www.hi138.com 10.3 trough at both ends of the slot insulation damage, carefully flip the termination part of the winding, insulation damage at the patience to find out, and then pad of paper and then coated with insulating varnish.

10.4 tank with iron filings and other debris are not divisible, wires embedded after pass to. Remove iron and other debris.

10.5 in the embedded line, the conductor insulation mechanical damage. Carefully pulled the termination part of the winding, insulation damage at the patience to find out, and then pad of paper and then coated with varnish insulation.

10.6 there is no reliable ground cover. Troubleshooting several ways according to the above, it will be grounded motor housing.

11, the motor insulation resistance decreased
The main reason for reducing motor insulation resistance and treatment
11.1 moisture ingress or rain drops in the motor. With a shake table to check was conducted after drying.

Too much dust and dirt on the winding 11.2. Remove dust, oil and after the impregnation.

11.3 pinout and connector junction box is about the aging of insulation. Re-bandaged head .7 KW Lead the following electrical wiring can be re-impregnation.

12, the common three-phase AC windings Burning Characteristics, Causes and Treatment
AC motor windings for the appearance of burning the cause analysis and put forward approach.

12.1 missing running
Repair of motor from the current work can be seen, because of missing running about the winding burned over 50% of the amount of repair.

Phase operation caused mainly due to wrong line and electrical wire connection, such as ceramic plug fuse, fuse link does not tighten the screws, or screw too tight and almost crushed the fuse, and there is the phenomenon of floating or the fuse around the copper contacts on the plug is not good, or bad electrical outlet side processing may not weld, etc., which are caused by high electrical resistance. As a large motor starting current, so that it caused the gradual oxidation circuit. due to lack of phase operation and burned the motor windings, the damage to the obvious characteristics of the motor discharge opening cover and saw the end of the motor windings 1 / 3 or 2 / 3 of the pole winding into a burning black or dark brown, while the remaining two-phase winding intact or slightly burned. the note is missing running caused.

Motor repair, use and defenders should always pay attention to the motor line, knife switch, fuse, outlet box, etc. The connection line, to be very reliable, qualified preferably magnetic starter, thermal relay or optional automatic right air circuit breakers, two-phase operation and prevent overload.

12.2 inter-turn short circuit
Off the assembly line when the motor manufacturing quality. End bumps, or more than the original design in parallel large ones, choose a wire diameter is too small, poor mechanical strength, end, or wire too thick and difficult to bend plastic, are easy to make insulation damage caused by inter-turn short circuit.

Due to inter-turn short circuit and burn the motor windings, which is characterized also more evident in the ends of the coil, can be clearly seen around a few turns or a pole-phase group or charred, this part of the magnet wire is often burnt bare copper wire, while the short circuit or some other than the two-phase winding us what are relatively intact or slightly charred.

Approach: to the local repair, replacement can be a circle or a group of coils. If the double-winding and insulation aging has been baked hard, or higher over the case slot, you should not turn local line, or all for the coil, the quality more is guaranteed.

12.3 short circuit between phases
Phase short circuit is often the end of the white insulation film, cloth or a double layer coil cushion pad is not a good article, or damp heat in the motor case, these weaknesses and insulation down to form the final breakdown phase short circuit. Also group together line pipe were not handled properly, or do not understand some of the motor built by PVC and other plastic casing of the heat resistance is poor, and to apply them in the motor windings, due to motor heating, so that the plastic melt, resulting in on-line short circuit .

Approach: change to the old winding. Attention to pad properly insulated and white, use the appropriate level of insulation materials and heat-resistant casing.

12.4 Grounding
Ground fault for many reasons, common are:
A high quality built off the assembly line 2 when the motor is not high quality machining high temperature or moisture 3 4 lightning.

Treatment:
A ground fault, check to see the obvious notch in the bottom of the burn or phenomena, such as can not see, can be found fault shake table:
1 belongs to the quality off the assembly line, in the re-coil is important to note for the original coil size is too small, if necessary, a slightly modified line-mode dimensions, improved wire or turns, slot insulation sufficient attention to the width and length.

Phase 2 is scheduled to rub the rotor, should be a good pre-mechanical parts, to prevent the coil burned again after the new ones.

3 due to high temperatures in insulation aging, and should use more high temperature magnet wire, slot insulation and other insulating materials, such as selection of B-class insulation. Also note that the original coil data is reasonable, pay attention to improving the quality of varnish, and increase the fan, reducing load and other cooling measures.

4, if you use more humid environment, should improve the quality of winding varnish treatment, do not use paper insulation, the use of film, linoleum, fiberglass insulation and other good water resistance, solvent-free paint or dip the ends of epoxy coating resin paint will be closed to prevent moisture into the windings.

Second, how the induction motor fault diagnosis and treatment
How to accurately determine and deal with various problems, in addition to master the basic principles of the theory of knowledge, more importantly, the repeated practice in the field, constantly sum up the experience accumulated on the fault of the check processing to achieve fast, accurate and good.

1. When the equipment fails,
One must first investigate the situation and to the management, operation and equipment failure were asked before and after motor operation and the failure of processes, phenomena, and then observe the accident scene to see whether the appearance of significant equipment damage or unusual odor, and then hand plate moving rotating parts, check it is flexible or loose, the sound, etc., can be a preliminary understanding of the extent of damage within the motor and the fault location.

2 found by the inspection but not the larger problem, and then measure the power supply voltage and check the insulation, such as the motor of the direct resistance, grounding resistance and so on.

3 Check the motor starting equipment and the control loop of some electrical equipment, such as: air switch, AC contactors, thermal relays, which are all right off and closed.

4 Check motor winding connection.

5 disassemble the motor coupling or pulley, starter motor no-load, view the motor body without fault. No-load testing, thoroughly inspect the sound, smell, vibration, temperature, current, voltage and speed and so on, according to actual situation make the right judgments.

Such as the no-load starting, the motor is not normal, you must open the motor body, look at the motor stator, rotor, windings, bearings and motor assembly of the various quality problems appear.

No abnormal phenomenon such as motor, the fault occurred in the drag on the machinery and equipment. There may be belt too tight, the load is too large or the coupling caused by improper assembly and other reasons, can be mechanical maintenance personnel in conjunction with dismantling the mechanical drag, elimination of obstacle point.

2. Detection equipment failure method
Visual inspection, by seeing, ears, nose and smell to find fault. See whether the charred outer surface, deformation, etc., listen to the sound operation of the motor, whether the phenomenon of noise and vibration. Smell the device is unusual odor. Not in the intuitive Judgement can be detected with instruments: a multimeter to measure line voltage available, current, resistance measurement bridge arms straight .2 .3 trillion Farm Table measurable resistance resistor .4 ammeter, voltmeter, current and voltage measurement device .5) three-phase current measurement clamp type ammeter. can determine whether the short circuit and open circuit line, turn to turn short circuit, grounding, winding insulation, rotor bar breaking fault and so on.

These above-mentioned common fault, sometimes it is not alone, there may exist a variety of reasons, and hope that we can to resolve the device into account the various issues. Links to Research Papers Download http://www.hi138 . com