Protective motor structure
The basic characteristics of this motor are: the base has a foot and two end cap bearings, generally adopting a bilateral symmetrical radial ventilation system (generally self-ventilating, can also be made into duct ventilation if necessary), and there is ventilation in the core. Road. The base is made of cast iron with longitudinal reinforcement at the inner circle to form a ventilation duct with the outer circumference of the core. For large-size motors, because of the heavy weight, there are two eyebolts on the top of the base. From the transmission end, the outlet box is in the middle of the right side of the base. The stator core of the large-size motor adopts an internal press-fit structure, that is, the punching piece is directly laminated in the frame. After stacking, use the pressure ring and the arc to tighten firmly in the axial direction.
The stator cores of the 3 kV and 6 kV motors use open slots, and the half or half closed slots are used below 500 volts. The end of the stator coil is tied with a spacer wire or tied with a polyester sheathed glass wire. For motors with higher speeds, the ends of the stator coils are also reinforced with insulated end clamps to enhance the ability to withstand the electromagnetic forces generated by the inrush current at start-up.
The rotor core is directly sleeved on the shaft, and is circumferentially and axially fixed by the flat key and the ring key. The yoke has an axial air passage for cooling; when the motor capacity is large, the rotor core is often mounted on the bracket, and sufficient axial air passage is left between the core and the bracket rib and the load. There is a pressing ring at each end of the rotor core (the pressing ring is fixed on the bracket by a curved key) for fastening and supporting the core end in the axial direction, and a groove for placing the balance block is opened thereon.
The rotor uses double-layered windings, which are inserted into semi-closed slots by semi-formed insulated copper bars (called semi-group coils), which are connected after bending; except for the slots in which the oblique conductors (also called jumper coils) are located. In addition, there are generally two conductors per slot. The ends of the coils are fastened with a matte glass ribbon. The lead wire of the rotor winding is passed through the center hole of the rotating shaft from the non-drive end and then connected to the slip ring. This shortens the distance between the bearings and reduces the deflection of the shaft. On the joint of the rotor half-group coil end, a plurality of blades are arranged and distributed equidistantly along the circumference as a fan.
The collector ring and brush unit are protected by a protective cover. When starting, the brush is in contact with the collector ring to connect the starting resistor. After the start is completed, the handle is pulled to the running position, the brush and the collector ring are divided, and the three collector rings are short-circuited by the short-circuit ring. Some winding type motors do not have a brushing device. At this time, the brush is always in contact with the collector ring, and the mechanical loss and brush wear increase during operation, but the motor structure is relatively simple.
Due to the large load on the drive end, a single row radial short cylindrical roller bearing is used there. The non-drive end uses a single row radial ball bearing. Roller bearings can also automatically adapt to the axial expansion caused by the expansion and contraction of the shaft due to changes in heat and cold and the machining and assembly deviations allowed by the components. In order to facilitate assembly and disassembly, and to keep the bearings clean during assembly and disassembly, both bearings are bearing sleeves.
