Quality inspection method of high voltage motor

Update:08 Jul 2022
Summary:1. Problems with welding parts such as leads and jointsDuring the manufacturing process or maintenance of the motor, pro...
1. Problems with welding parts such as leads and joints
During the manufacturing process or maintenance of the motor, problems such as virtual welding and incomplete welding will cause the welding point of the motor to be de-soldered during operation, resulting in a large contact resistance of the welding part. . This kind of problem mostly occurs in the parts that need to be soldered, such as the head cover of the inserted winding bar of the rotor coil, the lead wire of the stator and the rotor, and the terminal. In the factory, after the rivets fixing the motor stator and the casing fell off, the stator iron core turned an angle and the motor was burned. Therefore, it is necessary to put forward silver welding, phosphor copper (chemical Cu) welding or other special welding requirements for all the parts that need to be welded in the motor order contract to avoid similar accidents.
2. Slot wedge problem
In the manufacturing process of high-voltage motors, due to the lack of vacuum dipping process, the full rate of the slots in the iron core coil (winding) slots of the stator (composition: stator iron core, stator winding and frame) is not high, resulting in the coil in the iron core slot. The internal vibration is caused by electromagnetic force, which causes the slot wedge to vibrate and fall off, thereby causing an accident. At present, some domestic use new magnetic conductive materials to make slot wedges, although the effect is relatively obvious in improving motor characteristics and energy saving, but such problems will also occur in use.
3 Bearing problems
Sliding bearing structures are often used on larger motors. After years of use, I feel that although the sliding bearing structure is beneficial, it is more troublesome to use and maintain than the rolling bearing, especially in the case of a long production cycle, the sliding bearing needs to be frequently replenished with thin oil. It is also necessary to grind the bearing shell regularly, and control the clearance of the bearing shell during installation. If it is not handled properly, problems such as oil leakage and oil leakage will occur. The rolling bearing only needs to be regularly replenished with lubricating oil with an oil gun. If there is a problem, it only needs to be replaced. The supplier changes the bearing structure and changes it to a fully sealed rolling bearing, avoiding the original trouble of installation alignment and maintenance. The problem caused by the entry of dust is avoided, and the effect is satisfactory.
In the design of high-voltage motors, C3 type bearings with large clearance are generally used, and C4 type clearances are also used for larger motors.
In the process of use, it is found that the surface of the inner ring of some bearings has a bit-like abrasion phenomenon, which is mainly caused by the rotor shaft current caused by the rotor in the alternating magnetic field (definition: the field that transmits the magnetic force between objects), and the induced voltage produces eddy currents. After the induced current is grounded by the rotor shaft through the bearing and then through the motor casing, electric spark ablation will appear in the bearing to produce point-shaped pits, which will cause bearing vibration and wear (a basic type of component failure) failure, which will seriously cause Stator and rotor friction sweeping accident. A carbon (C) brush is installed on the motor rotor coupling, the brush holder is fixed on the motor end cover, and the shaft current is directly grounded, which can reduce or avoid the occurrence of such faults. In addition, the bearing supply channel (channel) must be reliable, so as to avoid the trouble of using the old and refurbished fake and inferior bearings. In addition, the lubricating oil of the bearing cannot be mixed, and the bearing must be lubricated according to the lubricating oil grade required in the technical specification, otherwise the bearing will be damaged.
4. The cooling problem of the motor
Large-scale high-voltage motors are designed with cooling devices, such as water cooling and air cooling devices. Generally, the coolers of water-cooled motors are placed on the top of the motor. Since the cooling water contains impurities, the heat exchange capillary of the cooler is It will cause scaling to block the capillary and affect the cooling effect of the motor. When cleaning the scale with chemical cleaning agents, the capillary will be corroded, so it must be checked after cleaning to confirm that there is no water leakage. The high-voltage motor is generated because the motor power is proportional to the product of the voltage and the current. Therefore, when the power of the low-voltage motor increases to a certain extent (such as 300KW/380V), the current is limited by the allowable bearing capacity of the wire, and the cost is too high. It is necessary to achieve high power output by increasing the voltage. High-voltage motors refer to motors with rated voltages above 1000V. The voltages of 6000V and 10000V are often used. Due to the different power grids in foreign countries, there are also voltage levels of 3300V and 6600V. The advantage of high-voltage motor is that it has high power and strong impact ability; the disadvantage is that the inertia is large, and it is difficult to start and brake. If the cooling water enters the motor and destroys the insulation, it will cause a short circuit between phases and ground (the current does not pass through the electrical appliance and is directly connected to the two poles of the power supply) Burned motor accident. During the operation and maintenance of the air-cooled motor, the cooling fan blades will be deformed, causing vibration during operation and damage to the motor, so attention must be paid.