Starting system for salient-poled-rotor electric motor

#The invention relates to the field of electric motors having a plurality of magnetic poles wherein the poles are alternately polarized and neutralized to produce rotation of a rotor, and more particularly, the present invention relates to salient-poled-rotor electric motors which have no coils or inductor bands on the rotor. The present invention further relates to start positioning systems for providing maximum starting torque for start-under-load conditions for such motors.

#In electric motors which have no coils or induction bands, successfully starting the motor under heavy loads can present some unique challenges. In the particular class of electric motors discussed herein, referred to herein as salient-poled-rotor electric motors, rotor torque is created by alternately creating a magnetic pole force in every other pole of the stator. For any three poles of the stator, the stator poles will alternate between a first state, wherein a pole force is exerted upon the rotor by the inner stator pole, but not by the outer two stator poles, and a second state, wherein a pole force is exerted upon the rotor by the outer two stator poles, but not by the inner stator pole. In such motors, the available torque between the rotor and the stator fluctuates between a minimum torque position, which nearly cancels all start torque, and a maximum torque position, which provides the greatest start torque, as each rotor pole moves in and out of register with respective stator poles. Thus, in developing starting torque, the position of the salient poles of the rotor in relation to the stator poles is the critical factor. The maximum torque position for the motor is to have the salient pole faces of the rotor positioned center of the stator pole slots, which places the face of each rotor pole halfway between two stator poles. In this position, each rotor pole face is half in register with one stator pole face and half in register with an adjacent stator pole face. The minimum torque position occurs where the rotor pole faces are all in register with a respective stator pole.

#The cancellation of start torque in the minimum torque position is created by magnetic flux from the stator poles from which the rotor poles are not in register. Thus, the stator poles to the right and to the left of any rotor pole both exert an attractive force on the rotor pole which is in register with the stator pole between them. The result is that the attractive forces that would otherwise induce the rotor to move are canceled by one another. In this balanced condition, there is near equal force to induce clockwise rotation as there is force to induce counter-clockwise rotation. The result is often only a vibrating rotor unable to achieve enough torque to move against the load.

#The description herein makes reference to the accompanying drawings wherein like referenced numerals refer to like parts throughout the several views and wherein:

#FIG. 1 is a partial schematic view of a motor stator in accord with the invention illustrating the direct current coils, only, being wound upon adjacent sets;

#FIG. 2 is a partial schematic view similar to FIG. 1 illustrating the alternating current coils wound upon the appropriate poles of the stator;

#Referring to the drawings, the present invention will now be described in detail with reference to the disclosed embodiment.

#In this disclosure, the effect of the invention will be called the Field-Match effect. The reason for the use of the word “match” is that it has two near opposite meanings: one which means “to agree, to be alike” (which we will designate “match1”) and another meaning which means “to oppose”, as in a “football match” (which we will designate “match2”). The torque produced by the stator on the rotor of the Split-Pole Field-Match Motor is caused by a unique design in which two coil fields of near equal value are matched on a single stator pole, alternately, in both senses of the word “match”.

#First, they are “matched1” in one part of the electrical phase as like-fields on the same pole which series and causes the pole to exert a magnetomechanical force on a laminated, ferrite, salient poled rotor; then the coils are “matched2” as opposing fields on the same pole in the opposite part of the electrical phase and the opposing magnetomotive forces exerted on the pole cause there to be no magnetomechanical force exerted on the ferrite rotor as no flux is manifested from the pole.