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The aim of this paper is to present a solution for active output voltage regulation in permanent-magnet (PM) automotive alternators, through mechanical flux weakening. An axial-flux PM ironless machine is investigated, which is composed of two stators connected in series which can be shifted one with respect to the other, thus allowing a theoretically infinite constant power speed range. This paper focuses on the aspects related to layout, sizing, and control of the shifting mechanism, which are critical for accurate output voltage regulation. Experimental tests on a 2-kW prototype validate the capabilities of the proposed solution, both during steady-state and transient operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, two methods for flux linkage regulation in a starter/alternator with an axial-flux permanent magnet (AFPM) machine are proposed and compared. Desired regulation is achieved by two different mechanical solutions, each of them capable of modifying the amount of flux linkage through displacement of the two rotors in the AFPM machine. Constant power generation is thus achieved with very inexpensive devices that do not require external energy sources since energy in the airgap doesn't change. The main difference between the two proposed solutions is that the speed dependant device is ideally a constant voltage source while the torque-dependant device behaves as a constant current source. Even if some improvements are still needed, both devices introduce the totally innovative concept of mechanical flux weakening for AFPM power regulation in a wide speed range. Finally, the paper demonstrates that the introduction of these devices doesn't modify machine behavior in starting mode, so that the particular features of AFPM machines in terms of high toque density and overload capability remain unaffected. [ABSTRACT FROM AUTHOR]

An ac brushless drive in which Hall-effect sensors are used as rotor position sensors is presented in this paper. Three different methods to obtain a high-resolution position estimation from the low-resolution sensors are described and compared through simulation and experimental testing. The proposed control algorithm's most innovative feature is its adaptability to the entire speed range, including startup, when using any of the three estimation algorithms. The control algorithm has been implemented and tested in order to drive a slotless axial-flux permanent-magnet (PM) machine for domestic appliance applications. [ABSTRACT FROM AUTHOR]