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This paper presents a new permanent-magnet (PM) brushless machine for wind power generation. This machine adopts an outer-rotor topology, aiming at capturing wind power directly. In order to achieve high power density, a high-speed PM brushless generator is artfully integrated with a coaxial magnetic gear. The design details, with emphasis on the special constraints of wind power generation, are elaborated. By using the time-stepping finite element method, the static characteristics as well as no-load and on-load operations are simulated. A prototype is also built for experimentation. Both simulation and experimental results are given to verify the validity of the proposed machine. Finally, a quantitative comparison is made to justify that the proposed machine is of smaller size, lighter weight, and lower cost than its counterparts. Index Terms--Finite-element method (FEM), magnetic gear, outer rotor, permanent-magnet (PM) machine, wind power generation.

Thermal models used in overload protection relays often fail to predict the rotor temperature for motors with impaired cooling conditions. In this case, the temperature estimated from the rotor resistance can be used as an indicator of the motor's cooling capability. However, this estimated rotor temperature is often corrupted by estimation error due to the asymmetry in the power supply. A detailed analysis of the trajectories of the complex current and voltage space vectors in a synchronous reference frame is presented in this paper, and the negative sequence fundamental frequency components are identified as the major cause of the estimation error. Based on this analysis, a fast and efficient algorithm is proposed to calculate the rotor temperature for line-connected induction machines. By applying the Goertzel algorithm to the complex current and voltage space vectors, constructed directly from the motor terminal measurements, the positive sequence fundamental frequency components are extracted, and the rotor temperature is then estimated with significantly reduced estimation error. Compared to the conventional scheme based on the fast Fourier transform, the proposed algorithm is faster and more efficient, and is therefore more suitable for implementation on a low-cost hardware platform. Index Terms--Complex space vector, condition monitoring, Goertzel algorithm, impaired cooling, induction machine, rotor temperature estimation, unbalanced supply.