This paper reviews the progress that has been made in the analysis and design of axial-flux permanent-magnet machines over the past decade, with particular attention to aspects such as electromagnetic and thermal modeling, materials, manufacturing, pulsating torque, and extended speed range. Comparisons with other machine types and applications are also reviewed
This paper presents the implementation and evaluation of a high-resolution position estimation system for sinusoidal, surface phase modulation machines based on Hall-effect sensors and a vector-tracking observer. First, the tuning of the observer is presented and a speed-dependent gain scheduling strategy is proposed. Then various harmonic decoupling strategies are investigated to improve the performance of the observer, particularly at low speeds. Stability analysis is performed leading to the definition of local stability limits, within which the actual position is tracked with bounded estimation error. Both simulation and experimental testing illustrate the performance and limitations of the proposed observer topology and of the drive when this observer is used for state feedback.
Axial flux permanent magnet (AFPM) machines are being increasingly used in a variety of industrial, direct drive applications which benefit from their extreme axial compactness. In particular, slotted AFPM machines are of great interest, since they allow to achieve high torque densities together with an adequate constant power speed range. This paper analyzes a particular aspect related to the design of such machines, i.e. the use of soft magnetic composite (SMC) wedges to close stator slots. Magnetic circuit-based analyses and 2-D and 3-D finite-element analyses are performed on a 10 kW AFPM machine; various magnetic wedge configurations are adopted; the no-load performance is compared with that of the same machine using nonmagnetic wedges in terms of flux linkage, cogging torque, and no-load losses. Finally, experimental tests and results on a full-scale prototype machine mounting magnetic wedges are reported
In this paper, binary Hall-effect sensor faults are investigated in rectangular-current-fed brushless DC drives and a very effective methodology for their detection, identification and compensation is explored. It is shown that these faults cause erroneous commutation, generally leading to unstable operation. By using a fault detection and identification technique proposed by the authors in a recent paper on low cost field-oriented drives, it is possible to pinpoint the faulty sensors. In this paper it is demonstrated that the destabilizing effect of these faults on motion state estimation can be compensated for in any position and speed estimation algorithm, as long as it is properly readapted. To this end, it is shown how to incorporate such faultcompensation in three state-of-the-art estimation algorithms: the zeroth order algorithm, the hybrid observer, and the vectortracking observer. Comparative experimental tests are performed and it is verified that stable operation is achieved with three, two or only a single Hall-effect sensor functioning correctly. These results show that the classical BLDC drive with three Hall-effect sensors has an inherent double redundancy to position-sensor faults. With the proposed method, this property can be exploited in systems that require very high reliability, such as in aerospace and automotive applications. Redundancy can be increased, by using more than three Hall-effect sensors; reduced by using two sensors; or eliminated by using a single sensor, in ultra low-cost applications where redundancy is not a requirement
The paper investigates methods for achieving really wide constant power speed range in electric drives. In particular, focusing the attention to hybrid excitation synchronous machines, five control strategies are presented and compared. It is shown how one of these allows for theoretically infinite constant power speed range. The strategies are also experimentally verified and a 10:1 range is demonstrated
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