Experimental Study on Relative Angle of Magnetic Pole and Its Driving Performance in Multi-Gap Type Variable Magnetic Flux PM Motors

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Abstract
This paper presents a variable magnetic flux PM motor in which space harmonic power is utilized for weakening the magnetic flux, automatically. The stator has a toroidally-concentrated winding structure, and the torque generation surfaces are composed of three air-gaps, including one single radial gap and two axial gaps. The radial-gap rotor is a constant-magnetized PM rotor and the axial-gap rotors are self-excited wound-field rotors. These rotors are coaxially fastened with opposite magnetic pole positions. The magnetomotive force of axial-gap rotor can automatically retrieve space harmonic power, which is inevitably generated by the concentrated winding structure. In this study, the effect of relative angle of the magnetic pole between the radial-gap rotor and the axial-gap rotors on the drive performance, e.g., current phase-vs.-torque characteristics, adjustable speed drive characteristics, and variable-magnetic-flux range, are experimentally demonstrated with a prototype machine.