Switching pattern ac induction motor

Abstract

Both the stator core and the rotor core of a switching pattern AC induction motor are fabricated by soft magnetic material laminations or ferrite material, etc., both of which have corresponding frequency characteristic. The excitation voltage is sine wave pulse width modulated or sine wave pulse amplitude modulated within the frequency range of voice and ultrasonic. Under the condition of the same power output, the present motor reduces its size and mass to a fraction of or tenth of that of an ordinary one. Meanwhile, it reduces the cost of manufacture. It realizes stepless speed regulating from zero to several thousand rpm while keeping well mechanical characteristic performance.

1 . A switching pattern AC induction motor comprising a machine base, a stator and a rotor, said stator including a core with stator teeth and grooves disposed alternately and excitation windings being disposed in the stator grooves, and said rotor being of a squirrel cage structure with metal conducting bars, 
 wherein the number of the stator grooves or teeth being determined by the following equation: Z=2*M*P*Q, where M being the number of phases of excitation voltages applied to the excitation windings, P being number of pairs of stator poles, and Q being the number of grooves or teeth per pole per phase;    said excitation windings on the stator of the motor being excited by a sine wave switching AC pulse modulated excitation voltages, and the number K of the metal conducting bars in the rotor ‘squirrel cage’ being twice of the number P of pairs of the stator poles, i.e. K=2*P*Q,    wherein, the sine wave switching AC pulse modulated excitation voltages are generated by performing pulse width modulation or pulse amplitude modulation on two phases of continuous modulating sine wave voltages with phase difference of 90 degree or three phases of continuous modulating sine wave voltages with phase difference of 120 degree with equal virtual values and frequencies, together with a pulse square wave voltage having a waveform of symmetric square wave with a duty factor of 50% of which the frequency (F 2 ) is within the frequency range of voice or ultrasonic and much larger than the frequency (F 1 ) of said continuous modulating sine wave voltages.    
   
   
       2 . The motor according to  claim 1 , wherein the frequency (F 1 ) of the continuous modulating sine wave voltages determines the rotation speed of the motor, and can be changed to perform speed control of the motor.  
   
   
       3 . The motor according to  claim 1 , wherein the resistance of the excitation windings of the motor is proportional to the frequency (F 2 ) of the pulse square wave voltage, and the higher F 2  is, the smaller the size and mass of the stator core, the rotor core and the windings of the motor are.  
   
   
       4 . The motor according to  claim 1 , wherein said motor is of a cylinder type by disposing said rotor on inner side and the stator on outer side, and said stator core is of cylinder shape, and said stator teeth are disposed on the inner surface of said stator core in equal angles and extending inward along a radial direction with stator grooves penetrating along an axial direction between the teeth, and said metal conducting bars of the ‘squirrel cage’ being disposed along the axial direction and distributed at equal intervals in parallel with a cylindrical surface of the rotor.  
   
   
       5 . The motor according to  claim 1 , wherein said motor is of a cylinder type by disposing said rotor on outer side and the stator on inner side, said stator core is of cylinder shape, and said stator teeth are disposed on the outer surface of said stator core in equal angles and extending outward along a radial direction with stator grooves penetrating along an axial direction between the teeth, and said metal conducting bars of the squirrel cage being disposed along the axial direction and distributed at equal intervals in parallel with a inner cylindrical surface of the rotor.  
   
   
       6 . The motor according to  claim 1 , wherein said motor is of a disk type motor, said stator core and said squirrel cage of said rotor are of a ring shape, and said stator teeth are disposed on a plane vertical to an axis of said ring shape along a radial direction on the surface of said stator core in equal angles with stator grooves penetrating along the radial direction between the teeth, and said squirrel cage includes metal conducting bars disposed along the radial direction and distributed at equal intervals and conducting rings to form a squirrel cage of a disk type.  
   
   
       7 . The motor according to  claim 1 , wherein, when the number of grooves or teeth per pole per phase is Q=1, the excitation windings on the stator adopt centralized windings with 1/M pole pitch or integral multiple pitch.  
   
   
       8 . The motor according to  claim 1 , wherein, when the number of grooves or teeth per pole per phase is Q>1, the excitation windings on the stator adopt distributed windings.  
   
   
       9 . The motor according to  claim 1 , wherein cores of the rotor and the stator are made by soft magnetic material laminations which meet corresponding frequency characteristics (F 2 ) within the frequency range of the pulse square wave voltage, and subject to surface insulation treatment, then to piling along the axial direction, or made of ferrite materials with corresponding frequency characteristic as a whole or in a manner of sectioning along the axial direction.  
   
   
       10 . The motor according to  claim 6 , wherein the stator core and the rotor core are made by belt-shaped soft magnetic materials which are subject to surface insulation treatment, and then wrapped along the axial direction to form a shape of disk, and treated along the radial direction to form grooves or teeth, or made of ferrite materials with corresponding frequency characteristic as a whole.