Motor repair methods, winding short circuit
Due to the motor current is too large, the power supply voltage varies too much, single-phase operation, mechanical bruises, poor manufacturing and other insulation damage caused by the sub-winding turn-to-turn short circuit, short circuit between the windings, short circuit between the windings, winding between the poles and the winding between the phases of the short circuit.
1. Failure phenomenon
Ion the uneven distribution of the magnetic field, the three-phase current imbalance and make the motor run vibration and noise, serious motor can not start, and in the short-circuit coil to produce a large short-circuit current, resulting in rapid heating and burned coil.
2. Causes
Motor overload for a long time, so that the insulation aging loss of insulation; embedded in the line caused by insulation damage; winding damp insulation resistance drop caused by insulation breakdown; end and interlayer insulation is not padded or shaping damage; end of the connecting line insulation damage; over-voltage or lightning strikes caused by insulation breakdown; rotor and stator winding end of the friction caused by the insulation damage; metal foreign objects falling into the internal and static windings. Metal foreign objects fall into the motor inside and too much oil.
3. Inspection methods
(1) external observation method. Observe the junction box, winding end with or without burning, winding overheating leaves dark brown, and odor.
(2) probe temperature inspection method. No-load operation for 20 minutes (should be stopped immediately when an abnormality is detected), with the back of the hand to feel whether the winding parts over the normal temperature.
(3) power experiment method. Measured with an ammeter, if a phase current is too large, indicating that the phase has a short circuit.
(4)Bridge check. Measurement of DC resistance of the winding, the general difference should not exceed 5% or more, such as more than, the resistance of a small phase has a short circuit fault.
(5) short circuit scout method. The measured winding has a short circuit, then the steel plate will produce vibration.
(6) multimeter or megohmmeter method. Measure any two-phase winding phase-to-phase insulation resistance, if the reading is very small or zero, indicating that the two-phase winding phase-to-phase short circuit.
(7) voltage drop method. Three windings in series connected to the low voltage safety alternating current, measured reading a small group of short-circuit fault.
(8) current method. Motor running at no load, the first measurement of three-phase current, in switching two-phase measurement and comparison, if not with the power supply switching and change, the higher current of a phase of the winding has a short-circuit.
4. Short-circuit processing methods
(1) short-circuit point at the end. Available insulating materials will be short-circuit points apart, can also be re-packaged insulated wire, and then paint re-drying.
(2) Short-circuit in the line slot. After softening, find out the short-circuit point repair, re-inserted into the line slot, and then paint and dry.
(3) for short circuit turns less than 1/12 of each phase of the winding, series turns when cutting off all the short circuit, the conductive part of the connection, the formation of a closed circuit, for emergency use.
(4) winding short-circuit point turns more than 1/12, to remove all the rewinding.
Second, the winding circuit
Because of poor welding or the use of corrosive flux, welding and not cleaned up, it may cause pot welding or loose; subject to mechanical stress or collision of the coil short-circuit, short-circuit and ground faults can also be burned wire, and burned in several wires in a few wires in a short-circuit or a few wires, the other several wires due to an increase in the current and the temperature rises, resulting in the winding heat And disconnection. Generally divided into a phase of the winding end of the broken wire, turn-to-turn short-circuit, parallel branch circuit at the broken circuit, more than one wire and burned in a broken circuit, rotor broken cage.
1. Failure phenomenon
Motor can not start, three-phase current imbalance, abnormal noise or vibration, temperature rise over the permissible value or smoke.
2. Causes
(1) in the overhaul and maintenance touched off or manufacturing quality problems.
(2) winding components, poles (phase) group and winding and lead wires, such as poor welding of the junction, long-term operation of overheating desoldering.
(3) Mechanical force and electromagnetic field force to make the winding damage or pull off.
(4) Turn-to-turn or phase-to-phase short-circuiting and grounding caused by serious scorching or fusing of the winding, etc..
3. Inspection method
(1) Observation method. Most of the breakpoints occur at the end of the winding, to see if there is a touch of folding, joints out of welding.
(2) multimeter method. The use of resistance gear, on the ?Y?-type connection will be a meter stick connected to the center of the ?Y?-shaped, the other connected to the first end of the three-phase winding in turn, infinity of a phase for the breakpoint; ? △? Type connection of the short open connection, respectively, measured each group of windings, infinity is the break point.
(3) test light method. The same method as before, such as a phase is not bright for the circuit breaker.
(4) megohmmeter method. Resistance tends to infinity (i.e., not zero value) of a phase for the break point.
(5) ammeter method. Motor in operation, with an ammeter to measure the three-phase current, if the three-phase current imbalance, and no short-circuit phenomenon, the current is smaller than a phase of the winding has a part of the short-circuit fault.
(6) bridge method. When the motor resistance of a phase than the other two phases of the resistance is large, the phase of the winding has a part of the break fault;
(7) current balance method. For the ?Y? type connection, the three-phase winding can be connected in parallel, through the low-voltage high-current alternating current, if the difference in current in the three-phase winding is greater than 10%, the current is small at the end of the circuit-breaking; for the ? △? type connection, the first stator winding of a contact split, and then phase by phase into the low-voltage high current, where the current is small phase for the circuit breaker.
(8) broken cage scout inspection method. When checking, if the rotor breaks the cage, the millivolt meter reading should be reduced.
4. Disconnection processing method
(1) When the disconnection is at the end, connect it and weld it firmly, wrap it with insulating material, put it on insulating tube, tie it and dry it.
(2) winding due to turn-to-turn, phase-to-phase short-circuit and grounding and other reasons for the winding serious scorching generally should be replaced with a new winding.
(3) the break point in the slot, is a small number of breakpoints to do emergency treatment, using the group elimination method to find out the break point, and in the winding of the broken part of the winding will be connected and insulation qualified for use.
(4) the cage rotor broken cage can be used to repair welding method, cold connection method or change the strip method.
Synchronous motor classification a. AC synchronous motor
AC synchronous motor is a constant speed drive motor, its rotor speed and power supply frequency to maintain a constant proportionality, is widely used in electronic instruments and meters, modern office equipment, textile machinery and so on.
Two, permanent magnet synchronous motor
Permanent magnet synchronous motor belongs to the asynchronous start permanent magnet synchronous motor, its magnetic field system consists of one or more permanent magnets, usually welded with cast aluminum or copper cage rotor, according to the required number of poles mounted with a permanent magnet poles. The stator structure is similar to that of an asynchronous motor.
When the stator winding is connected to the power supply, the motor is started by the principle of asynchronous motor, accelerated to the synchronous rotational speed, the synchronous electromagnetic torque generated by the rotor permanent magnetic field and stator magnetic field (electromagnetic torque generated by the rotor permanent magnetic field and stator magnetic field generated by the reluctance of the rotor torque synthesis) the rotor will be drawn into the synchronous motor into the synchronous operation.
Resistance Synchronous MotorResistance Synchronous Motor, also known as reactive synchronous motor, is a synchronous motor that generates reluctance torque by using unequal reluctance of rotor cross-axis and straight-axis magnetic resistance, whose stator structure is similar to that of asynchronous motor, only the rotor structure is different.
Three, reluctance synchronous motor
The evolution of the same cage-type asynchronous motor, in order to make the motor can produce asynchronous starting torque, the rotor is also equipped with a cage-type cast aluminum winding resistance. The rotor is equipped with a reaction slot corresponding to the number of stator poles (only the role of the convex pole part, no excitation windings and permanent magnets), used to generate reluctance synchronous torque. According to the different structure of the reaction slot on the rotor, it can be divided into internal reaction rotor, external reaction rotor and internal and external reaction rotor, of which, the external reaction rotor reaction slot is open to the outer circle of the rotor, so that the straight axis and the direction of the intersection of the axes of the air gap is not equal. The inner reactive rotor has grooves on the inside, so that the magnetic flux in the direction of the intersection axis is blocked and the magnetic resistance is increased. The internal and external reactive rotor combines the structural characteristics of the above two rotors, and the difference between the straight and intersecting axes is large, so that the force energy of the motor is large. The reluctance synchronous motor is also divided into single-phase capacitor-run, single-phase capacitor-starting, single-phase double-value capacitor type and other types.
Four, hysteresis synchronous motor
Hysteresis synchronous motor is the use of hysteresis material to produce hysteresis torque and work of synchronous motor. It is divided into internal rotor type hysteresis synchronous motor, external rotor type hysteresis synchronous motor and single-phase shaded pole type hysteresis synchronous motor. Internal rotor type hysteresis synchronous motor rotor structure for the hidden pole type, the appearance of a smooth cylinder, no winding on the rotor, but the core on the outer circle of the ring made of hysteresis material effective layer.
The classification and types of electric motors 1. According to the type of working power supply: can be divided into DC motor and AC motor.
1) DC motor according to the structure and working principle can be divided: brushless DC motor and brush DC motor.
Brush DC motor can be divided into: permanent magnet DC motor and electromagnetic DC motor.
Electromagnetic DC motor division: series-excited DC motor, parallel-excited DC motor, other-excited DC motor and compound-excited DC motor.
Permanent magnet DC motor division: rare earth permanent magnet DC motor, ferrite permanent magnet DC motor and alnico permanent magnet DC motor.
2) which AC motors can also be divided: single-phase motors and three-phase motors.
2. According to the structure and working principle can be divided: can be divided into direct current motor, asynchronous motor, synchronous motor.
1) synchronous motor can be divided into: permanent magnet synchronous motor, reluctance synchronous motor and hysteresis synchronous motor.
2)Asynchronous motors can be divided into: induction motors and AC commutator motors.
Induction motor can be divided into: three-phase asynchronous motor, single-phase asynchronous motor and shaded-pole asynchronous motor.
AC commutator motor can be divided into: single-phase series-excited motor, AC and DC dual-use motor and push repulsion motor.
3. According to the starting and running mode can be divided into: capacitor starting single-phase asynchronous motor, capacitor running single-phase asynchronous motor, capacitor starting running single-phase asynchronous motor and split-phase single-phase asynchronous motor.
4. According to the use can be divided into: drive motor and control motor.
1) drive motor can be divided into: power tools (including drilling, polishing, grinding, slotting, cutting, reaming and other tools) with electric motors, home appliances (including washing machines, electric fans, refrigerators, air conditioners, tape recorders, VCRs, video recorders, video disk players, vacuum cleaners, cameras, hairdryers, electric shavers, etc.) with electric motors and other general-purpose small machinery and equipment (including a variety of small machine tools.), Small machinery, medical equipment, electronic instruments, etc.) with electric motors.
2) control motors are divided into: stepper motors and servo motors.
5. According to the structure of the rotor can be divided into: cage-type induction motor (the old standard called squirrel cage asynchronous motor) and wire-wound rotor induction motor (the old standard called wire-wound asynchronous motor).
6. According to the operating speed can be divided into: high-speed motor, low-speed motor, constant-speed motor, speed motor. Low-speed motors are further divided into gear motor, electromagnetic reduction motor, torque motor and claw pole synchronous motor.
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