1 repair and maintenance of motor stator winding
1. 1 winding requirements of motor stator winding
Winding is one of the main components of motor and the key part of energy conversion. It is composed of many coils, all of which are placed in the stator core slot, and then connected in series or parallel to form a motor winding according to certain rules. Whether the winding design is reasonable or not will affect the torque, speed, loss, efficiency and temperature rise of the motor. Therefore, the following requirements are put forward for motor windings: ① the potential and magnetic potential of each phase winding should be symmetrical, and the resistance and reactance should be balanced, that is, the three-phase winding structure is exactly the same; (2) shortening the connection part, saving copper and reducing the short-circuit loss of the winding; (3) The winding has good heat dissipation and reliable insulation and mechanical strength; ④ The winding structure has good construction technology.
Several important parameters of 1.2 motor winding
1.2. 1 polar distance. The range occupied by each magnetic pole along the inner circle of motor stator core is called pole pitch.
1.2.2 pitch. The number of slots spanning between the two effective sides of the winding element is called the pitch.
1.2.3 electrical angle. Electrical angle = polar logarithm? 360? .
1.2.4 number of slots per pole and phase. Number of slots occupied by each phase winding under each pole.
1.3 Types of motor windings
1.3. 1 Composition principle of three-phase stator winding:
In the three-phase stator winding, the number of coils in each phase is equal and the arrangement is the same, and the interval between phases in the slot is 120? The electric angle conforms to these two principles, that is, it constitutes a three-phase symmetrical winding, and only in the three-phase symmetrical winding can a balanced three-phase electromotive force be induced.
1.3.2 Three-phase stator winding includes single-layer winding and double-layer winding.
There is no interlayer insulation problem in the single-layer winding slot, so there will be no interlayer and interphase insulation breakdown fault in the slot. Convenient winding and embedding; The disadvantage is that the selection of short-distance coils is limited and the electromagnetic waveform is not ideal, so it is generally used in low-power motors, and its coils are scattered coils wound with circular electromagnetic wires into multiple turns. The advantage of double-layer winding is that the suitable short-distance coil can be selected at will, and the technical index of the motor is better than that of single-layer winding, which is generally used for large and medium-sized motors.
1.4 replacement and repair of motor stator winding
1.4. 1 winding of coil
① Loosening coil: Loosening coil is wound with insulated coil wire, and its geometric size is guaranteed by winding die, and it must be made into appropriate size, and the tension should not be too large. The wires should be arranged in sequence in the wire mould; The uneven crossing of wires not only makes it difficult to bury wires, but also easily leads to turn-to-turn short circuit fault; During the winding process, the broken wire should be welded on the hypotenuse of the coil end, and the joint is not allowed to stay in the coil slot.
② Forming coil: Forming coil is more complicated than loose coil. Usually, when repairing and replacing coils, spare coils are used or coils are ordered from the manufacturer according to the motor model.
1.4.2 Offline, connect and check. Preparation before off-line: including insulation materials and coil, slot wedge, welding materials, slot insulation preparation, iron core cleaning, cleaning and sanitation of the work site, etc. At the same time, you must be familiar with the drawings and clearly understand the number of motor poles, winding pitch and lead direction. To avoid errors when offline.
1.4.2. 1 The offline process of embedded winding is as follows:
① The lower edge of the lower first pitch coil. Determine the position of the first slot based on the buckle slot of the iron core or the outlet hole of the base, embed the lower coil edges one by one, and pad the upper coil with cardboard;
② Embedding the remaining coils. After lowering the lower edge of the coil, pad the insulation between the upper layers, lower the edge of the upper coil into the groove with the corresponding pitch, straighten the edge of the coil in the groove with a scribing board, gently press the end by hand to prevent warping, then fold the groove insulation and drive it into the groove wedge;
(3) lowering the coil with the last pitch, raising the upper edge of the coil with the first pitch, lowering the lower edge of the coil with the last pitch, lowering the upper edge of the coil with the next pitch, folding the groove for insulation, and driving into the slot wedge;
(4) End shaping: Use rubber hammer or bamboo board to make the end into a bell mouth with appropriate diameter. Too small will affect the insertion, ventilation and heat dissipation of the rotor, too large will make the end too close to the casing and affect the motor insulation;
⑤ End dressing. Trim the insulating paper with the same end neatly;
⑥ Insulation test. Check whether the tightness and insulation of the slot wedge with protruding size at the end are damaged, and carry out withstand voltage test on interphase insulation and ground insulation;
⑦ Interpolar connection. Pressing the same coil? Positive string? Or? String? Specify the connection, lead out the cable, weld it firmly, wrap the insulation, and then tie the connecting wire tightly;
8 Check and test. Check the wiring and welding quality;
Pet-name ruby dipping paint. Dip paint and dry, and spray insulating paint on the surface of the winding.
65438+ wiring
① Press a single coil at 60? Phase bands are allocated and connected into polar phase groups;
(2) connecting pole-phase groups in the same phase to form windings of each phase;
(3) Lead the beginning and end of the three-phase winding to the junction box with wires, and all joints shall be welded and insulated.
1.4.2.3 test
Check the stator winding before painting, including: ① whether the winding is grounded; ② Whether the winding is short-circuited; ③ Whether the winding is open; (4) Whether the winding is wrong or upside down.
After confirming that there are no above problems, dip it in paint and dry it.
1.4.3 paint impregnation and drying
After the stator winding is rewound or partially replaced, the gaps between the winding and the iron core and between wires can be filled with insulating paint, so that the winding and the iron core form a whole. The moisture-proof performance of the winding is enhanced, and the insulation strength, heat dissipation capacity and mechanical strength of the winding are improved. Therefore, the paint dipping and drying of stator winding is a very important process of motor repair, which roughly includes the following processes;
1.4.3. 1 pre-baking:
The function of pre-baking is to drive away the moisture in the winding, which is usually carried out in an oven, and the temperature is controlled at 120? About 4 hours -8 hours. Measure the insulation resistance of winding to ground with a 500V shaking table every1h. When the insulation resistance value is stable, pre-baking can be completed.
1.4.3.2 impregnation:
When the temperature of the sub-core to be measured drops to 60℃-70℃, it can be dipped in paint. When dipping the paint for the first time, the viscosity of the paint should be lower so that the insulating paint can penetrate into the winding as much as possible. For the second dipping, the viscosity should be higher, so as to form a thicker paint film on the winding surface. In general, the method of coating can be used, and it should be repeated several times evenly.
1.4.3.3 drying
Drying is to volatilize the solvent and moisture in the paint, so that a stronger paint film can be formed on the winding surface. The drying process is preferably divided into two processes. ① Low temperature stage. The temperature is controlled at about 70-80 DEG C for 2-4 hours; ② High temperature stage. The temperature is about 130℃, about 8h~ 16h, so as to form a firm paint film. At this time, the insulation resistance of the winding to the ground should be measured with a 500V shaking table every 1h, and the insulation resistance should be stable at 5M until the last 3 hours. Above, the winding is dry.
1.4.4 Repair of stator winding end wear
The stator winding of AC motor is acted by alternating electromagnetic force in operation, because the electromagnetic force generated between its adjacent windings is proportional to the square of the current flowing through it. Therefore, in the process of starting, short circuit and locking, the maximum electromagnetic force sometimes reaches dozens of times the normal value. Therefore, the winding end structure cured by end painting is easy to cause insulation wear, which is a very common fault of AC motor. The reason for this is the following：
① The thermal shrinkage of the end binding rope after thermal curing is not enough, and the winding ends of each phase cannot be tightened after the paint is cured, resulting in that the winding ends cannot be bound and fixed firmly in the direction of stress and vibration. Therefore, once the motor is subjected to alternating tangential force and axial force, the stress point is added to the contact between the winding and the end binding, causing vibration displacement. This is one of the main reasons for accelerating the insulation wear at this place;
(2) When off-line, the binding end causes damage to the end insulation pressing line;
(3) The paint curing process at the end can't guarantee the rigidity of the cured rope;
(4) When the gap in the slot increases, the coil vibrates in the slot, causing the coil to wear at the slot.
1.4.5 local repair of stator winding. If one or part of the motor winding is burned, local maintenance should be considered. First, find out the exact fault point of the faulty coil, heat the motor winding to 100℃- 130℃ to soften the winding insulation, and then remove the slot wedge and the faulty coil while it is hot. When removing the old coil, be careful not to damage the intact coil. After the faulty coil is removed, replace it with a new coil, then drive it into the slot wedge and soak it in paint to dry.
2 Troubleshooting of motor core
2. 1 Function of motor core
The iron core of the motor is not only the key component of electromagnetic energy conversion, but also bears the comprehensive effects of mechanical vibration, electromagnetic force and heat in the motor. In order to reduce the eddy current loss in the core, it is necessary to have a certain insulation resistance between the core laminations.
2.2 Repair of common faults of iron core
2.2. 1 The single tooth of the iron core tooth pressing plate opens outward in the axial direction.
This is because the teeth of the toothed plate are uneven when the iron core is laminated, and the punching sheet appears wavy after the iron core is pressed, and the teeth of the iron core are tilted, or the rotor contacts the stator core to pry up individual teeth of the toothed plate when it is pulled out. When restoring, just use a copper bar to knock out individual teeth that open outward.
Local burn of iron core
The arc generated when the winding has a phase-to-phase short circuit or a ground short circuit fault sometimes burns out the iron core locally. If the burned area is not large, the iron core can be repaired without disassembly. First, use files, chisels, grinding wheels and other tools to level or level the local burned parts of the iron core, then peel off the silicon steel sheets one by one with a knife, coat a layer of self-drying insulating paint on the surface of the iron core, and then compact the iron core. If the burned area is large, replace the iron core or the damaged punch.
Radial looseness of iron core
Radial looseness of iron core has the following two situations:
(1) The small motor with external press-fitting iron core technology is caused by loose fit between the outer circle of the iron core and the inner hole of the frame, or loose positioning screws between the iron core and the frame. The repair method is to tighten the positioning screw, add another positioning screw on the frame if necessary, or weld the iron core on the frame;
(2) Large and medium-sized motors with internal pressure iron core installation process are caused by loose opening of the radial positioning device of the iron core or desoldering of the welding place between the iron core and the frame. The repair method is to fasten the positioning device, install the locking screw or repair the welding at the desoldering position.
Fault treatment of squirrel-cage rotor
Broken bar is a common fault of squirrel-cage asynchronous motor, mostly the joint between copper bar and end ring, which can be cleaned and welded with silver.
In addition, the rotating shaft often has some defects. For example: the rotating shaft is bent; Wear of keyway and bearing seat, etc. According to different situations, these problems can be solved by straightening the welding handle, milling the keyway again, electroplating or spraying a layer of chromium on the bearing seat.
Motor water 1 maintenance skills. Evaporate water with a hot air gun.
If the motor wheel is made of aluminum, its inner magnetic steel surface will be dried with a hot air gun, and the water will be evaporated! If the surface of magnetic steel is oxidized and rusted after being wetted, give it to the motor? Internal force? Large loss leads to large discharge current and motor heating, which wastes electricity! After a long time, sludge and rust will gather, and the bearings inside the motor will be easily damaged and swept away! The increase of motor current riding has a negative impact on the shortening of continuous mileage, and the large motor friction will cause the whole vehicle parts to run hard!
2. The hot air gun blows dry the accumulated water in the stator winding.
Dry the accumulated water in the stator winding with a hot air gun, and install it when the insulation resistance of the winding is greater than 10 megohm. Pay attention to Hall when the hot air muzzle blows the stator, and don't let the high temperature turn Hall over? Dissolve, otherwise the hall will be "baked" after the water dries, and the installation and operation will be abnormal.
3. Observe the two end covers of the motor.
Observe whether the two end covers of the motor are rusted, stuck or inflexible due to water ingress. What if it doesn't work? Properly lubricate and replace it in time if necessary to avoid bearing damage to the motor. Steel eggs? Fall off and break the coil, resulting in scrap!
4. Sealing treatment of both ends of motor cover