The wrong maintenance method of motor winding leads to incomplete rotating magnetic field, difficult starting, unbalanced three-phase current, loud noise and other symptoms. In severe cases, if not handled in time, the winding will be burned out. There are mainly the following situations: one or more coils of a certain pole phase are embedded reversely or the head and tail are wrongly connected; Pole (phase) group inversion; Inverted winding; Multi-path parallel winding branches are wrongly connected; ? △? 、? y？ Wrong connection.
1, failure phenomenon
The motor can't start, the no-load current is too large or unbalanced, the temperature rises too fast or vibrates violently, the noise is loud, and the fuse is blown.
2. the reason
Misleading? △? Type connection? y？ Type; During maintenance, one phase of the three-phase winding is connected end to end; Decompression start-up is improper tap position selection or internal wiring error; When the new motor goes offline, the winding wiring is wrong; The old motor's judgment is wrong.
3. Maintenance methods
(1) ball method. If the ball rotates and rolls along the inner circumferential surface of the stator, it is correct, otherwise the winding is wrongly connected.
(2) Compass method. If the windings are not wrongly connected, when the compass passes through adjacent pole (phase) groups in one-phase winding, the polarities should be opposite, and the adjacent pole (phase) groups in different phases in three-phase winding should also be opposite; If the polarity direction remains the same, it means that one pole (phase) is connected backwards; If the direction is uncertain, there are reverse coils in the phase group.
(3) Multimeter voltage method. According to the wiring diagram, if the voltmeter does not indicate twice, or there is one reading and one reading, it means that the winding is connected backwards.
(4) Dry battery method, milliammeter remanence method and motor steering method are also common.
4. Processing method
(1) If a coil or coil group is connected reversely and the no-load current is unbalanced, it should be repaired in the factory.
(2) If the outgoing line is wrong, it should be reconnected after the head and tail are judged correctly.
(3) If the decompression starts incorrectly, carefully check the wiring diagram or schematic diagram and reconnect.
(4) If the new motor is offline or reconnected with new windings, it should be sent to the factory for repair.
(5) When the stator winding is connected reversely, the reverse one-phase current is particularly large, so the fault can be found and repaired according to this characteristic.
(6) release? y？ Type connection? △? Type or number of turns is not enough, and the no-load current is large, so it should be corrected in time.
Maintenance method of short circuit of electrical winding: insulation damage caused by excessive motor current, excessive change of power supply voltage, single-phase operation, mechanical collision and poor manufacturing, such as inter-turn short circuit, inter-winding short circuit, inter-pole short circuit and inter-phase short circuit of windings.
1. Fault phenomenon
The uneven distribution of ion magnetic field and unbalanced three-phase current aggravate the vibration and noise of the motor during operation. In severe cases, the motor can't be started, but a large short-circuit current is generated in the short-circuit coil, which leads to the rapid heating and burning of the coil.
2. the reason
The motor is overloaded for a long time, which makes the insulation aging lose its insulation function; Insulation damage caused by wire embedding; The winding is damp, which reduces the insulation resistance and leads to insulation breakdown; During the molding process, the insulating materials at the ends and between layers are not filled or damaged correctly; The insulation of the end connection wire is damaged; Insulation breakdown caused by overvoltage or lightning strike; Friction between rotor and stator winding ends leads to insulation damage; Foreign metal objects fall into the motor, resulting in excessive oil pollution.
3. Inspection method
(1) external observation method. Observe whether the junction box and winding end are burnt, and the winding still has dark brown and odor after overheating.
(2) Temperature detection method. Run at no-load for 20 minutes (stop immediately if any abnormality is found), and touch with the back of your hand whether all parts of the winding exceed the normal temperature.
(3) charged experimental method. When measuring with ammeter, if a certain phase current is too large, it means that there is a short circuit in this phase.
(4) Bridge inspection. When measuring the DC resistance of each winding, the general difference should not exceed 5%. If it exceeds 5%, the phase with small resistance has a short circuit fault.
(5) Short circuit detector method. If the winding is short-circuited, the steel plate will vibrate.
(6) Multimeter or megger method. Measure the interphase insulation resistance of any two-phase winding. If the reading is very small or zero, it means that there is a short circuit between the phases of the two-phase winding.
(7) Pressure drop method. After the three windings are connected in series, low-voltage safe alternating current is applied, and the group with small reading is found to have short circuit fault.
(8) Current methods. When the motor is running at no load, measure the three-phase current first, and then measure the two-phase comparison when it is changed. If it does not change with the change of power supply, the single-phase winding with large current is short-circuited.
4. Short circuit treatment method
(1) The short circuit point is at the end. The short-circuit points can be separated by insulating materials, or the insulated wires can be repackaged, repainted and dried again.
(2) The short circuit is in the wire slot. After softening, find out the short circuit point for repair, put it back in the tank, and then paint it to dry.
(3) For each phase winding with short-circuit turns less than112, when the turns are connected in series, the short circuit is completely cut off, and the conductive parts are connected to form a closed loop for emergency use.
(4) When the number of turns at the winding short-circuit point exceeds112, all windings shall be dismantled and rewound.
The motor of electric vehicle is the power mechanism of electric vehicle, and its performance directly affects the overall performance of electric vehicle. Maintenance must be carried out. Detect the wear degree of brushes and commutator of electric vehicles. Generally, the brush should be replaced when it is worn to a distance of 4 ~ 5 mm from the lead, and when the surface depth of the commutator is greater than 0.5mm, it should be replaced. For the motor in normal use, no matter how serious the wear is, the brush and commutator should be replaced regularly (usually two years).
Whether it is a brush electric vehicle motor or a brushless electric vehicle motor, its excessive input current will affect its performance. The voltage of the motor is provided by the controller. The aging of electronic components in the controller will lead to the increase of current input of the motor. Therefore, the controller must be checked and replaced if necessary.
Regularly lubricate the gears, bearings and deceleration parts of electric vehicle motors. If the inner and outer sleeves of gears and bearings are excessively worn, the vibration isolator is deformed, and the spring performance is degraded or broken, the controller should be replaced. Pay attention to charging the battery of electric vehicle frequently, so that the battery can keep enough voltage, prevent the motor from heating due to insufficient voltage, and accelerate the aging of the motor of electric vehicle.
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