Study on the Generating Mechanism of a Parametric Oscillation in the Laminated Core Parametric Motor

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Since 1979, the authors have been engaged in the development and research of practical applications for an orthogonal core parametric motor that offers numerous attractive features not found in conventional motors. In 1995, the authors succeeded in manufacturing a laminated core parametric motor that can be mass-produced using conventional production facilities. This motor is comparable to conventional single-phase induction motors with respect to both output and efficiency.However, at low speeds, a parametric oscillation has become unstable in some cases and the torque has dropped to zero. This is a serious problem for the practical use of the motor.In this research, the author has studied the generating mechanism of a parametric oscillation in order to find the method of stabilizing the parametric oscillation and solve the problems noted at low speeds.The following results were obtained :(1) Forming the stator of a laminated core parametric motor in an asymmetric shape is highly effective in stabilizing the parametric oscillation and in improving the motor characteristics like output and efficiency.(2) The asymmetry of the inner ring of a stator influences on the characteristics of the motor such as output and efficiency. The asymmetry of the outer ring of the stator influences on the stability of the parametric oscillation.(3) When the angle between adjacent magnetic poles is shifted by 10 to 15 degrees from the basic angle 90 degrees, the parametric oscillation is stabilized, the "normal-reverse rotation" region disappears, and the output and efficiency of the motor are largely improved.(4) The qualitative analysis of the motor was carried out based on the nonlinear differential equation obtained from the magnetic circuit model of the motor. The main reason of stabilization of the parametric oscillation is that a portion of the primary flux flows into the secondary magnetic circuit.