Abstract—Improvements on the torque with low currents using rotor with spiral sheets are analyzed. Several rotors and stators have been built combining different constructive and mechanical characteristics of the related elements: inertias, constructive materials, geometrical shapes of the sheets and geometrical disposition of the sheets. These different types of motors have been simulated using computer aided tools and then tested in the laboratory. Finally, four stators (1000, 1500, 1500-type A, and 3000 rpm) having the same constructive parameters, have been simulated and tested with the following rotors types: solid rotor, solid rotor with diamagnetic rings, drag cup, and simple and double squirrel cage rotor; these results have been compared to those obtained with the seven variants of spiral sheet rotor presented in this paper.
Index Terms—Electric machines, Special machine, Spiral sheet rotor, Three-Phase asynchronous motor.
Technical Tracks—T2: Electrical machines and drives.
I. INTRODUCTION
The rotors of conventional asynchronous motors are formed by magnetic sheets packed above the shaft of the machine. The rotating magnetic field created by the stator, induces currents parallel to the shaft and so upright to the rotor sheets [1]. Those currents cannot flow between the sheets if they are electrically isolated, being necessary the intervention of conventional squirrel cage rings to close the electric circuit and thus the rotor currents can circulate.
In table I the basic mechanical characteristics of some rotors tested are presented [3]. These rotors have the same dimensions and they are assembled to stators of 1000 rpm, 1500 rpm and 3000 rpm, having the latter the same constructive parameters.
II. MOTOR WITH SPIRAL SHEET ROTOR
Forming a rotor with spiral shape sheets [8], distributed in a radial disposition around the shaft, it is possible to generate a magnetic field in the rotor periphery, inducing peripheral emf, and currents along the same sheets, that are only active in their periphery.