Repair method of motor 1 Winding short circuit
Insulation damage is caused by excessive motor current, excessive power supply voltage change, single-phase operation, mechanical collision, poor manufacturing and other reasons, including turn-to-turn short circuit, winding short circuit, inter-pole short circuit, winding phase-to-phase short circuit and so on.
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.
Second, the winding is open
Failure to clean after welding may cause pot welding or looseness due to poor welding or corrosive flux; 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.
Classification of synchronous motors I. AC synchronous motors
Ac synchronous motor is a kind of constant speed drive motor, and its rotor speed keeps a constant proportional relationship with power frequency, which is widely used in electronic instruments, modern office equipment, textile machinery and so on.
Second, the permanent magnet synchronous motor
Permanent magnet synchronous motor belongs to asynchronous starting permanent magnet synchronous motor, and its magnetic field system consists of one or more permanent magnets. Usually, in the cage rotor welded by cast aluminum or copper bars, the magnetic poles embedded with permanent magnets are installed according to the required number of poles. Stator structure is similar to asynchronous motor.
When the stator winding is energized, the motor starts to rotate according to the principle of asynchronous motor. When it is accelerated to synchronous speed, the synchronous electromagnetic torque generated by the rotor permanent magnetic field and the stator magnetic field (the electromagnetic torque generated by the rotor permanent magnetic field is combined with the reluctance torque generated by the stator magnetic field) pulls the rotor into synchronization, and the motor enters synchronous operation.
Reluctance synchronous motor Reluctance synchronous motor, also known as reactive synchronous motor, is a synchronous motor that generates reluctance torque by using the unequal reluctance between the horizontal axis and the direct axis of the rotor. Its stator structure is similar to that of asynchronous motor, but its rotor structure is different.
Three, reluctance synchronous motor
The same squirrel-cage asynchronous motor has also developed. In order to make the motor produce asynchronous starting torque, the rotor is also provided with cage-type cast aluminum windings. There are reaction slots corresponding to the number of stator poles on the rotor (only salient poles are used, and excitation windings and permanent magnets are not used) to generate reluctance synchronous torque. According to the different structure of the reaction tank on the rotor, it can be divided into internal reaction rotor, external reaction rotor and internal and external reaction rotor. Among them, the reaction tank of the external reactive rotor is open to the outer circle of the rotor, so that the air gap in the direction of its direct axis and horizontal axis is not equal. The internal reactance rotor has grooves, which block the magnetic flux in the transverse direction and increase the magnetic resistance. The internal and external reaction rotors combine the structural characteristics of the above two rotors, and there is a big difference between the direct axis and the cross axis, which makes the motor have greater force energy. Reluctance synchronous motor is divided into single-phase capacitor operation, single-phase capacitor starting, single-phase dual-value capacitor and other types.
Four, hysteresis synchronous motor
Hysteresis synchronous motor is a synchronous motor that uses hysteresis material to produce hysteresis torque to work. It is divided into inner rotor hysteresis synchronous motor, outer rotor hysteresis synchronous motor and single-phase pole-wrapped hysteresis synchronous motor. The rotor structure of internal rotor hysteresis synchronous motor is hidden pole and its appearance is smooth cylinder. There is no winding on the rotor, but there is an annular effective layer made of hysteresis material on the outer circle of the iron core.
Classification and type of motor 1. According to the type of working power supply, it can be divided into DC motor and AC motor.
1) DC motors can be divided into brushless DC motors and brushed DC motors according to their structures and working principles.
Brushed DC motors can be divided into permanent magnet DC motors and electromagnetic DC motors.
Electromagnetic DC motors are divided into series excited DC motors, parallel excited DC motors, separately excited DC motors and compound excited DC motors.
Permanent magnet DC motors are divided into rare earth permanent magnet DC motors, ferrite permanent magnet DC motors and Al-Ni-Co permanent magnet DC motors.
2) Among them, AC motors can also be divided into single-phase motors and three-phase motors.
2. According to the structure and working principle, it can be divided into DC motor, asynchronous motor and synchronous motor.
1) synchronous motors can be divided into permanent magnet synchronous motors, reluctance synchronous motors and hysteresis synchronous motors.
2) Asynchronous motors can be divided into induction motors and AC commutator motors.
Induction motors can be divided into three-phase asynchronous motors, single-phase asynchronous motors and shielded pole asynchronous motors.
AC commutator motor can be divided into single-phase series motor, AC -DC dual-purpose motor and repulsion motor.
3. According to the starting and running modes, it can be divided into three types: capacitor-started single-phase asynchronous motor, capacitor-operated single-phase asynchronous motor, capacitor-started single-phase asynchronous motor and split-phase single-phase asynchronous motor.
4. According to the purpose, it can be divided into drive motor and control motor.
1) drive motors can be divided into: motors for electric tools (including drilling, grinding, polishing, slotting, cutting, reaming, etc. ), motors for household appliances (including washing machines, electric fans, refrigerators, air conditioners, tape recorders, video recorders, DVD players, vacuum cleaners, cameras, hair dryers, electric razors, etc.). ) and other general small mechanical equipment (including various small machine tools).
2) Control motors are divided into stepper motors and servo motors.
5. According to the rotor structure, it can be divided into squirrel-cage induction motor (old standard called squirrel-cage asynchronous motor) and wound rotor induction motor (old standard called wound asynchronous motor).
6. According to the running speed, it can be divided into high-speed motor, low-speed motor, constant-speed motor and variable-speed motor. Low-speed motors are divided into gear reduction motors, electromagnetic reduction motors, torque motors and claw-pole synchronous motors.
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