The maintenance method of motor winding open circuit may cause pot welding or looseness because of poor welding or corrosive flux, which is not cleaned after welding; The short circuit, short circuit and grounding fault of the coil under mechanical stress or collision will also burn out the conductor. When one or several wires are short-circuited, due to the increase of current, the temperature of other wires rises, causing the winding to heat up and open. Generally, it can be divided into single-phase winding end break, turn-to-turn short circuit, parallel branch open circuit, multiple wires burned out by one-time open circuit, and rotor broken cage.
1. Fault phenomenon
The motor cannot be started, the three-phase current is unbalanced, there is abnormal noise or vibration, the temperature rise exceeds the allowable value or smoke.
2. the reason
(1) Damage or quality problems during overhaul and maintenance.
(2) The winding elements, pole (phase) groups, windings and leads are poorly welded, and they are overheated and desoldering after long-term operation.
(3) The winding is damaged or broken by mechanical force and electromagnetic force.
(4) Turn-to-turn or interphase short circuit and grounding lead to serious burning or fusing of windings.
3. Inspection method
(1) observation method. Breakpoints often occur at the end of winding, depending on whether there is bump or fracture, and whether there is desoldering of joint.
(2) Multimeter method. Use resistors, right? y？ Connect the watch stick to? y？ At the center point of the shape, the other one is connected to the head end of the three-phase winding in turn, and the infinite phase is the breakpoint; ? △? After short-circuit connection by T-connection, measure each winding separately, and the infinite winding is the disconnection point.
(3) Test lamp method. The method is the same as before, and the unlit phase is an open circuit.
(4) Megger method. The phase where the resistance tends to infinity (i.e. non-zero value) is the breaking point.
(5) ammeter method. When the motor is running, measure the three-phase current with an ammeter. If the three-phase current is unbalanced and there is no short circuit phenomenon, the winding with smaller current has some short circuit faults.
(6) Bridging method. When the resistance of one phase of the motor is greater than that of the other two phases, it indicates that the winding of this phase has a local open circuit fault;
(7) Flow balance method. For what? y？ T-connection, three-phase windings can be connected in parallel, and low-voltage and high-current alternating current can be introduced. If the current difference in the three-phase winding is greater than 10%, the end with small current is open; For what? △? T-connection is to disassemble a contact of stator winding first, and then connect low voltage and high current in turn, and the phase with low current is open circuit.
(8) Inspection method of broken cage detector. During the inspection, if the rotor damages the rotor cage, the reading of the millivoltmeter should be reduced.
4. Open circuit treatment method
(1) When the terminal is disconnected, it should be welded firmly after wiring, covered with insulating material, covered with insulating tube, bound and dried.
(2) If the winding is severely burned due to turn-to-turn and interphase short circuit and grounding, a new winding should be replaced.
(3) Emergency treatment is carried out for a few breakpoints with breakpoints in the slot, and the breakpoints are found by grouping exclusion method, which will be used after the winding is disconnected and connected with insulation.
(4) The broken cage of cage rotor can be repaired by welding, cold joining or changing bars.
Maintenance method of motor water inlet 1. If the motor wheel of an electric vehicle is made of aluminum, blow dry its inner magnetic steel surface with a hot air gun to evaporate water! 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. 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 water will dry up and the installation and operation will be abnormal!
3. Observe whether the two end covers of the motor are rusted, stuck or influxed, resulting in inflexible rotation. 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. It is best to apply sealant around the motor end cover to avoid secondary damage caused by lax sealing! Check the motor end covers on both sides of the motor? Oil seal? Is it completely closed, so that water can enter as seamlessly as possible!
Precautions for motor use 1. All circuits and electrical connections of the motor of electric vehicles are designed and guided by professionals, and users are not allowed to modify and connect them themselves, otherwise failures and accidents (including serious consequences such as fire and traffic accidents) will easily occur.
2. Although all kinds of electrical appliances and components of electric vehicles have certain waterproof function, the waterproof performance will be reduced due to damage and aging, so electric vehicles should not run on the road surface with water depth that can immerse the motor shaft. When parking or driving in the rain, cover all kinds of switches, knobs and other parts with a rain cover to prevent these electrical equipment from being damaged by moisture.
3. If the motor is found to have fever (above 90℃), smoke, peculiar smell, abnormal sound or other abnormal phenomena, it should be stopped immediately and sent to our distribution point for treatment. Do not disassemble the motor by yourself.
4, should avoid the vehicle in the case of overload, insufficient tire pressure or driving on a long and steep slope, otherwise the motor is in danger of burning.
5. The electric wheel hub shall not be violently impacted, and the electric vehicle shall not be forcibly started in a blocked state. When the electric vehicle can't be started due to obstacles, don't start it repeatedly, and start the motor after removing the obstacles of the electric vehicle.
6. For motors equipped with chains, remember to fill the chain with lubricating oil frequently, which can not only reduce the wear and tear of transmission parts, prolong their life, but also reduce the transmission noise.
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