Common problems with ac motor
Prevention: (1) remove the pulsating flux and the power supply harmonic (such as the ac reactor in the output side of the converter); (2) when the motor is designed, the bearing seats and the base of the sliding bearings are insulated, and the outer and end of the rolling bearings are insulated. 2, why can't the general motors be used for plateau areas? At altitude, the commutation of the electric motor, the electric corona (high voltage motor) and the dc motor are adversely affected. The following three aspects should be noted: (1) high elevation, the larger the motor, the smaller the output power. But when the temperature rises with elevation, it is sufficient to compensate for the effect of elevation The rated output power of the motor is constant.
Why does the motor produce shaft current? The shaft of the motor - the shaft bearing seat - the current in the base circuit is called the shaft current. The cause of axial current generation: (1) magnetic field asymmetry; (2) there are harmonics in the electric current; (3) the manufacture and installation is not good, because the rotor eccentric causes the air gap to be uneven; (4) there are gaps between the two semi-circles of the removable stator iron core; (5) the number of scalloped iron cores that have a fan stack is not appropriate. Harm: make motor or ball bearing surface erosion, shape process, microporous worsen bearing operation performance, the friction loss and heat increase, resulting in Bearing burn out.
?the high voltage motor shall adopt anti-corona measures in the use of the plateau; (3) the high altitude is unfavorable to the dc motor, and the carbon brush material should be chosen. Why is the motor not suitable for light load? When the motor is light, it will cause: (1) the power factor of the motor is low. (2) the motor is inefficient. It will cause equipment waste and run uneconomic. (1) excessive load; (2) lack of phase; (3) the wind tunnel is blocked; (4) the slow running time is too long; (5) the power supply is too large. 5, why can't you start the machine in a cold environment? The motor is too long in low temperature, it will be: (1) the electrical insulation cracking; (2) the bearing grease freezes; (3) wire joint solder powder. Therefore, the motor should be kept in cold environment, and the winding and bearing should be checked before operation. What are the reasons for the imbalance of the electric current? (1) the three-phase voltage imbalance; (2) bad welding or poor contact of a certain phase of the motor; (3) short circuit in motor winding, or short circuit to ground or phase. (4) connection error.
?the bearing room is too big. (3) tighten the screws; (4) there is clutter in the motor. Electromagnetic aspect: (1) the motor is overloaded; (2) the three-phase current imbalance; (3) missing phases; (4) stator, a short circuit failure of the rotor winding; (5) the welding part of the cage rotor welding is caused by cutting. What are the causes of overheating of motor bearings? The motor itself: (1) the inner and outer ring of the bearing is tightly coupled; (2) there is a problem with the parts, such as seats, ends, shafts, etc. (3) improper bearings; (4) the bearings are not lubricated or the bearings are not cleaned, and the grease contains sundries; (5) shaft current. Usage: (1) the unit is improperly installed, such as the shaft of the motor shaft and the shaft of the device that is dragged. (2) the pulley was pulled tight; (3) the bearing is not well maintained, the grease is not sufficient or exceeds the use period, and the hair dries out. What is the cause of low electrical resistance? (1) the windings of the winding or water intrusion; (2) gathering dust or oil on the windings; (3) aging of insulation; (4) the insulation of the motor lead or the junction plate.
