1. The generation, damage and preventive measures of the shaft voltage of high voltage motor The high-voltage motor generally has a large capacity, and its volume is large, and the magnetic circuit imbalance is likely to occur during manufacture, such as the difference in magnetization characteristics of the silicon steel sheet, the unevenness of the air gap, and the like. In addition, the stator winding is unbalanced, the three-phase power supply is unbalanced, the field winding is short-circuited, and the asynchronous motor is broken. These can cause the stator core of the motor to generate an alternating magnetic field around the core, so that an induced alternating voltage appears on the rotating shaft of the motor, which is the shaft voltage. When the shaft voltage reaches a certain value, it can break through the oil film of the bearing and generate a shaft current through the end cap casing or the bearing housing to form a loop. The shaft current can cause spot burns on the rollers and journals of the bearing bush and the journal or bearing, and even damage the normal operation of the bearing in severe cases. In order to block the current circuit, for the motor with the bearing housing, an insulating pad is usually placed under the bearing seat of the counter load end, and the fixing screw of the shaft bearing is also provided with an insulating sleeve. In motors with end cap bearings, if a plain bearing is used, an insulating mat is placed between the bearing shell and the shoe seat; if a rolling bearing is used, an insulating partition is provided on the bearing sleeve, and the fixing screw of the bearing sleeve is also carried. Upper insulation sleeve. The other is to directly use bearings with insulation, but the cost is higher. 2. Common causes of high vibration during operation of high voltage motors The vibration of the motor, especially the vibration of the high-speed motor exceeds the standard limit, which will affect the normal operation of the motor and even damage the motor, causing the unit to stop abnormally and affect production. The vibration value and vibration frequency of the motor are measured using a spectrum analyzer or a vibration tester, and the measurement data is analyzed to diagnose the cause of the motor vibration. The motor is repaired for the cause of the vibration, which can reduce the blindness of the inspection, complete the inspection in the shortest time, and return the motor to normal. Roots motor generates vibrations of electromagnetic vibration and mechanical vibration, electromagnetic vibration inherent vibration motor, this is not considered, the mechanical vibration of the motor is generated vary with the motor running and maintenance vibration can be eliminated, so in this primary analysis motor Mechanical vibration. Mainly due to mechanical vibration of the motor body in two parts, i.e., the support portion of the rotor part of the motor, the rotor of the motor. Cause motor rotor vibration caused deformation of the rotor core, the rotor shaft is bent, the concentricity of the rotor core and rotor bearing stopper outer exceeded, or the size of the rotor bearing block undesirable abrasion, loose rotor balancing block, open the Rotor Huigou the uneven falling off. Cause rotor support portion of the motor cover by the motor causes vibration deformation, deformation of the bearing sleeve, a motor end cap bore or belt wear sleeve within the bore of the bearing motor bearing, bearing damage and the like. 3. The generation of corona phenomenon of stator coil of high voltage motor and preventive measures The voltage stator coil of the high-voltage motor has an uneven electric field distribution on the insulating surface at the venting groove and the end of the slot. If the local field strength reaches a high value (non-uniform critical field strength 8.1 kV? Mcm), localized ionization (glow discharge) occurs. At the ionization there will be a blue fluorescence called a corona phenomenon. When the rated voltage of the high voltage motor reaches 6kV and above, the stator coil begins to generate corona. Corona produces thermal effects and oxides of ozone and charcoal, which prevent insulation. Therefore, measures should be taken to prevent corona from occurring in high voltage motors with rated voltages of 6 kV and above. Insulating the coil surface of the groove portion and then through the low-resistance corona preventing treatment layer, so that the ventilation slots electric field distribution can be made uniform, reducing the axial field strength; also antihalation layer and the low pressure at the contact resistance of the groove wall at a low potential, Short-circuit the gap here. If the resistance of the anti-halation layer is low and the anti-halation layer is stably grounded, the gap between the insulating surface layer and the groove wall can be short-circuited without corona. However, in order to reduce the loss of the antihalation layer, the resistance of the antihalation layer is not suitable for too low, so that the antihalation layer far from the contact point is not at a low potential, and becomes a capacitor current on the low resistance antihalation layer. The potential determined by the resulting voltage drop is generally a thermoplastic insulated coil. When the resistivity of the antihalation layer reaches 104-105, the corona can be substantially avoided. The end coil will refer to the semiconductor anti-halation layer of the first-order or second-order constant resistivity, or the anti-halation layer of the primary and secondary silicon carbide can prevent the corona at the end of the end and the corona at the end. . 4. High-voltage motor end cover easy to generate faults and treatment methods The end caps of high-voltage motors are usually equipped with bearing sleeves except for the small power or volume. When the end caps and bearing sleeves are released by long-term stress and their own stress, they will be deformed, resulting in the motor not being able to be used normally. When the motor bearing runs the outer casing, the inner hole of the end cover or the inner hole of the bearing sleeve is worn out, and the size becomes large and cannot be used. The process of spraying is similar to the insert, except that the material of the sleeve is replaced by a sprayed metal material. There are three treatment methods: 1 re-making spare parts, 2 pairs of inner holes for nesting treatment, and 3 pairs of inner holes for spraying and then processing. When remanufacturing spare parts, in addition to the size of the original size or within the same tolerance level, it is necessary to pay full attention to the possibility that the new spare parts may have unreleased stress and the size is deformed again. The thickness should not be less than 5mm, and there should be positioning measures between the sleeve and the body, and the metal material coated with the spray should be replaced. Correction during processing is very important, in addition to ensuring that the inner hole is the same as the outer circle of the outer ring or the sleeve, and that the inner control axis is perpendicular to the plane of the end cap, and for the bearing sleeve, the sleeve and the end cap are guaranteed. Install the joint surface perpendicular to the inner hole. 5. Judgment and treatment of rotor cage broken bar fault of high voltage motor After the rotor cage of the high-voltage asynchronous motor is broken, the rotor magnetic field is unbalanced, so that the magnetic field is unbalanced. This causes the motor output to drop and the efficiency to decrease. At this time, the motor exhibits a decrease in the rotational speed, the stator current rises, and the temperature rise is high. This phenomenon is particularly noticeable when the motor load is heavy. Therefore, when this phenomenon occurs, the rotor cage of the motor should be inspected. When the broken strip is confirmed, the rotor cage should be recast aluminum or replaced with a copper strip. 6. Motor insulation resistance is low After the high-voltage motor stops working for a period of time, it is necessary to check the insulation strength before starting. Otherwise, the insulation breakdown will occur shortly during the start-up operation. At this time, the megohmmeter will be used first. The F-class insulation grade, the voltage is above 6000V. Using a 2500V megger, the motor is well insulated and its insulation value is greater than a few hundred megaohms. The insulation strength of a 6kV motor can be controlled at 1MΩ/1kV in the cold state. If it is found to be lower than 1MΩ/1kV, the motor cannot be started. Determine the reason why the insulation resistance of the high voltage motor is low. 1 The water inside the motor is damp. The high voltage motor needs to be dried. If you stop working for too long and inhale a lot of moisture to make the motor damp, you must dry it and disassemble the motor into the drying room for drying. 2 If there are impurities and dust on the windings, clean the inside of the high voltage motor. 3 The motor insulation winding is aging. It is necessary to check the insulation of the lead wire and restore or replace the insulated wire board of the junction box, check the aging of the winding and replace the winding. Pp Self Wrap Braided Sleeve,Custom Pc Cable Sleeving,Pc Cable Sleeving Kit,Pc Sleeved Cable Extensions Shenzhen Huiyunhai Tech.Co., Ltd. , https://www.cablesleevefactory.com
Common faults and treatment methods of high voltage motors
Through the principle, structure and problems that are easy to occur in the operation of high-voltage motors, we can achieve more discoveries, more observations, more analysis, and more summarization. Strictly perform standardized maintenance in the work, so that high-voltage motors can be safe, stable, long, full, and excellent. The operation ensures the normal production of production equipment and brings greater economic benefits to the enterprise.