| The single-winding double-speed asynchronous motor is a kind of pole-changing adjustable-speed motor which can change the number of the pole in order to vary the speed. Because the number of pole only can be integer, it is belong to stepped speed regulating. Compared with the frequency control, its range and performance of speed regulation are limited, but the single winding and double-speed asynchronous motors are still widely used in the field which is not need high performance of speed regulating, such as fans and compressed water pump. Its greatest advantage is energy-saving.In this research, based on the investigation and study of mass of references, the development of the theory of variable-pole AC windings and the applications of adjustable-speed asynchronous motor with variable-pole are discussed. The characteristic of the single winding and double-speed asynchronous motor is presented and the methods of varying poles are analyzed in detail. There are two approaches to realize the pole-changing: inverse pole-changing and phase conversion pole-changing. Both of the methods are presented in the second chapter, and correlative design cases are shown followed. The comparisons between them are put forward. The cases of pole-changing of a 4/6 poles single-winding double-speed asynchronous motor are gained using the methods and the comparison of the harmonic component of windings magnetic potential shows that the case of changing 60? belt span 4 poles to 90? belt span 6 poles with connection method of 4Y/3Y is the optimally result.The single winding and double-speed asynchronous motor can not be designed according to the method of general single -speed asynchronous motor yet. There are some differences including the selection of the primary dimension, the slot coordination, the choosing of pitch, dimension choosing of yoke respectively. The relational expressions between the torque, the power and the air-gap magnetic flux density with different number of poles are deduced and the specific computation is carried out at last. |
