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This paper compares the electromagnetic performance of 10-MW superconducting (SC) generators with three different topologies, i.e., iron-cored stator and rotor topology (ISIRT), iron-cored stator and air-cored rotor topology (ISART), and air-cored stator and rotor topology (ASART). The objective is to provide a powerful insight into the advantages and disadvantages of different topologies, and to establish some design guidelines for selecting an appropriate direct-drive SC generator for offshore wind turbine applications. First, the structures of the three SC generator topologies are introduced. Then, the influence of the SC coil cross-sectional area on torque capability is compared. After that three SC generators with different topologies are optimized, respectively, for further comparison, including the active material cost, weight, harmonics in the electromotive force, torque ripple, field harmonics in the SC coil, and forces on the rotor and stator components, etc. It is found that, with the same SC quantity, the torque capability of the ISIRT is much better than that of the other two topologies. However, the advantage becomes less significant when a larger area of the SC coil is employed. The air-gap flux density waveform of the ASART is much smoother than those of the ISIRT and ISART. The torque ripples of the ISIRT and the ISART are much higher than that of the ASART. The field harmonics (both amplitude and frequency) in the SC coil of the ASART are the lowest. For the ISIRT, most of the force on the rotor is acting on the rotor iron, and thus, the SC coil is more likely to be safe from a mechanical performance point of view and the design of the corresponding supporting structure is simple. However, for the air-cored rotor topologies, nearly all the force is acting on the SC coil. For the air-cored stator, the force mainly acts on the armature winding, whereas for the iron-cored stator, it is mainly on the stator teeth. Due to the excellent mechanical performance of iron, the iron-cored stator is therefore more robust. [ABSTRACT FROM PUBLISHER]

This paper investigates the influence of pole number and stator outer diameter on the performance of superconducting (SC) generators. The SC generator has an iron-cored rotor topology. First, the generator structure is introduced and the optimization procedure is described. Then, the influence of design parameters on performance, in terms of generator volume, weight, SC wire utilization, active material cost, etc., is presented. Some relationships for the optimal combinations for different performance attributes are established. In addition, the influence of SC material price on the determination of optimal stator outer diameter and pole number is discussed. Finally, the influence of SC coil area per pole on performance is also investigated. [ABSTRACT FROM PUBLISHER]

This paper proposes a methodology to improve the reliability of diagnosis of different types of faults in wound-rotor induction generators which work under variable load conditions, as in wind turbine applications; the method is based on the extraction of the instantaneous frequency (IF) of the fault-related components of stator and rotor currents during speed changes caused by nonstationary functioning. It is shown that, under these conditions, the IF versus slip plots of the fault components are straight lines with a specific slope and y-intercept for each kind of fault. In addition, neither of these patterns are dependent on the machine features or the way that the load changes. The practical methodology of this technique is introduced for diagnosing two different anomalies: stator winding asymmetry and rotor winding asymmetry. The approach is validated by laboratory tests for both types of faults in two different kinds of machines. [ABSTRACT FROM PUBLISHER]