Box type motor
This is a newly developed and promising structural type in recent years. It has been widely used in AC and DC motors abroad, especially in medium and large asynchronous motors.
The main components of the box motor are the cover, base, stator, rotor and bearings. The outer cover is light in weight because it does not bear any load. It can be integral or composed of upper and lower parts. Generally, for a split-half housing, the lower half of the housing of the same frame motor is the same, but the upper half of the housing varies with the motor protection type and cooling method. The base is required to have a high strength because it has to withstand the weight of the entire motor and the related force. The motor bearing can adopt rolling bearing or sliding bearing according to the situation. The bearing seat is divided into upper and lower halves at the center of the shaft to facilitate disassembly.
The advantages of the box structure are mainly (1) the versatility of the parts is high (for example, the base, the core, the bearing housing, etc. can be used universally). (2) It is easy to derive a motor with different protection type and cooling method by using only different covers, which is easy to standardize. (3) The stator core is externally pressed, so that the stator core press, the lower line, the dipping, the processing of the base and the outer cover can be simultaneously performed, the production cycle is shortened, and the whole vacuum and pressure impregnation process is facilitated to improve the insulation quality. (4) The machining amount is small, the air gap uniformity is high, the down line is convenient, and the disassembly is easy.
Since the 1970s, China has begun to adopt this structure in medium-sized asynchronous motors, but there are still some problems that need further research and resolution. For example, there are currently two structures, the air-conditioning gap and the non-adjustable air gap, which are better to be studied. The former is simpler to machine, but the total assembly workload is large; the latter does not necessarily have less machining work than the conventional structure, and requires some special machine tools. Secondly, with the box structure, the number of cast iron pieces is small and the amount of steel sheets is increased. In addition, in terms of total manufacturing hours, there is a significant reduction in high-voltage motors, but an increase in low-voltage motors.
