Multiphase induction motor drives - a technology status review

The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operatio

Conceptualising the role of evaluation systems in markets: the case of dominant evaluators

Evaluation is usually an internalized process that is intrinsic to the activities of market actors. Producers evaluate what goods to produce, intermediaries such as distributors and retailers evaluate what goods to promote and stock, while consumers evaluate what goods to buy. In some cases, however, a secondary evaluation market controlled by an external evaluator can emerge as a de-facto gatekeeper exerting a powerful influence over the activities of market actors in the primary market. This article develops a conceptual model of external evaluation that describes: (i) the factors common to primary markets that are dominated by evaluation markets; (ii) the characteristics common to dominant evaluators and their evaluation markets; and (iii) the dynamic processes through which an evaluator can become entrenched in a position of dominance over other market actors. This conceptual model is illustrated through examples drawn from three dominant evaluators and the markets they dominate

Quartz oxygen isotopes from Tick Hill area in Mount Isa Inlier: indication of a regional fluid overprint

At the Tick Hill gold deposit, δ18Oquartz data for the mineralised lithologies and surrounding rocks are similar and fall within a narrow range of 10.5–13.7‰ V-SMOW. The highly mineralised quartzo-feldspathic mylonite has quartz δ18O (δ18Oquartz) values of 11.3–13.6‰, which are similar to values for the surrounding rocks both locally and regionally, i.e. δ18Oquartz by itself does not provide a useful exploration tool. The δ18Oquartz values from the Tick Hill area most likely reflect the late Isan hydrothermal overprint at 1525–1520 Ma. The origin of the altering fluids is unclear, as the δ18Oquartz values overlap with reported δ18O values calculated for both metamorphic and igneous fluids. When combining the δ18Oquartz results with δ18Ocalcite results available from the literature, a temperature of 350–550 °C was calculated, which is consistent with observed alteration assemblages associated with gold mineralisation