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The concern for energy conservation opens up a very large market for adjustable speed drives of medium to large rating. This paper advocates the increased use of neodymium-based permanent magnet motors in these drives based on their potential for a higher efficiency than can be achieved with induction motors. Typically, it is estimated that the losses of the permanent magnet motor can be made less than 60% of those of an induction motor of the same frame size. The result is a saving in electric energy costs which may compensate for the higher initial cost of the motor in less than a year of operation. >

A comprehensive approach to the analysis and design of GTO-CSI (gate turn-off thyristor-current source inverter) induction machine drive systems with rotor frequency control is presented. To overcome difficulties associated with the design of this nonlinear, nonminimum-phase, and high-order drive system, various analytical tools are employed. These tools include a root locus approach, eigenvalue analysis, eigenvalue sensitivity analysis, and time-domain simulation. A systematic design procedure for the drive system is developed, and a detailed design example is presented. Experimental results on a 800-HP prototype drive system are given for the verification of the theoretical work. >

In permanent magnet (PM) synchronous machines, iron losses form a larger portion of the total losses than in induction machines. This is partly due to the elimination of significant rotor loss in PM machines and partly due to the nonsinusoidal flux density waveforms in the stator core of PM machines. Therefore, minimization of iron losses is of particular importance in PM motor design. This paper considers the minimizing of iron losses of PM synchronous machines through the proper design of magnets and slots, and through the choice of the number of poles. Both time-stepped finite element method (FEM) and the iron loss model from a previous study are utilized in this paper to draw the conclusions.

Permanent magnet (PM) motors offer potential energy savings as compared with induction motors because of the virtual elimination of rotor loss and the reduction of stator loss from operation near unity power factor. In PM machines, iron losses form a significant fraction of the total loss partly due to the nonsinusoidal flux density distribution. Design optimization therefore requires good means of predicting these iron losses. Finite element analysis can be employed but this approach is cumbersome and costly when used in the many iterations needed in optimizing the design. This paper presents a set of improved approximate models for the prediction of iron loss. They can be used in design optimization programs and, since they are directly related to machine dimensions and material properties, they also provide quick insight into the effects of design changes. A time-stepped finite element method is employed to evaluate the iron losses in a range of typical PM machines and the results are used to evaluate the adequacy of the models. The predictions of overall iron losses are then compared with measurements made on two PM motors.

It is scarcely news to readers of this volume that the heterogeneous field of ‘post-colonial studies’ is reproducing itself at present as a spectacle of disorderly conduct. Perhaps this is as it should be for a field which takes for its academic objective a wholesale refashioning of the Western project of the traditional ‘humanities’; but I think it is clear that the institutionalized field of post-colonial studies, at least, has arr ived at a point of multiple intersections, of ruptures, of territoriality-and this suggests that the field has arrived at a point that really matters in its history. In this essay, I want to try to think through the dis/order imbricated in the post-colonial academic field, and in part to respond to the ways in which a policing energy seems to carry itself across a variety of articulations within the postcolonial problematic. The policing energy which interests me here is in the final instance an internalized apparatus for control and regulation, an effect of ideology, and I am not about to argue that ‘out there’ in post-colonialdom there are double agents, neocolonialist conspirators, wolves-in-sheep’s-clothing, whom ‘we’ must resist through some vigorous form of oppositional collectivity. But I am going to suggest that as the field of post-colonial studies is becoming professionalized as an institution for social critique and as an apparatus for producing cultural knowledge, it is beginning to perform within itself a regulating operation which has no necessary relation to, or investment in, a politics of anti-colonialism. This article, consequently, is an attempt to carry out some (ideological) refereeing in this structure of professionalized or disciplinary regulation: I want to address the question of who gets to play on the post-colonial field, who is asked to sit on the bench, who plays on the farm team, how and when a player is, or ought to be, called‘out’. Now obviously, I am in no sense outside of these questions; I too have an institutional stake in this game and am part of the disciplinary scramble. My refereeing persona here must necessarily be ambivalent, compromised by a double articulation in meta-regulation and in wager. Nevertheless, for the purposes of this exercise, I want to pretend to stand somehow outside the ‘field’.

It is pointed out that the conventional approach to core loss prediction using the Fourier series of the space wave of air gap flux density is not applicable to surface mounted permanent magnet (PM) motors. An alternative approach based on the concept that eddy current losses are proportional to the square of the time rate of change of the flux density is presented. Expressions are derived for predicting hysteresis and eddy current losses in the stator teeth and yoke. Prediction of core losses is compared with measurement of losses on a four-pole PM motor, confirming the applicability of the proposed approach. >

Revision du concept de realisme magique : lecture de " The Invention of the World " (Jack Hodgins), " What the Crow Said " (Robert Kroetsch), " Middlewatch " (Susan Kerslake) et " Two-Strand River " (Keith Maillard)

Adam von Fulda, German musician, composer and teacher, completed his important treatise on music in 1490. While representing a conservative, northern tradition in late-medieval music theory, it also shows some evidence of humanist influence. The treatise is divided into four books which discuss the origins and uses of music, the theory of plainchant, mensuration and notation of rhythm, and proportions, respectively. Thus, throughout this informative work, Adam mixes the practical with the speculative. Although his style of explaining technical matters is clear and succinct, he also engages the reader's interest with his polemical and rhetorical digressions. This dissertation presents a detailed commentary upon Book II of the treatise, on musica plana (plainchant), accompanied by a translation from the Latin. The first two chapters of the dissertation are concerned with the biographical information available on Adam von Fulda, as well as with the format and transmission of the treatise. Three chapters of the dissertation serve as the commentary. Chapter III discusses Adam's treatment of the practical aspects of singing plainchant, including his discussions of the Guidonian hand, the gamut, the naming of pitches, hexachords and mutation (material covered in Chapters 1 to 6 of the treatise's second book). Chapter IV of the dissertation considers the subject of musical intervals as covered by Adam, and the ten rules of composition provided in his Chapters 7 to 12. These rules are perhaps the most interesting and unusual part of Book II, as they go beyond the stated subject of plainchant. Written composition, not just improvised counterpoint, is treated in a manner that anticipates later humanist regard for music as an art. Finally, Chapter V examines Adam's treatment of the modes of plainchant (discussed in his Chapters 13 to 17). A conclusion summarizes Adam's impact on later theorists and the importance of the treatise.

A detailed analysis of a pulse-width modulated AC-to-DC voltage source converter under the proposed predicted current control with a fixed switching frequency (PCFF) is presented. It includes a steady-state analysis, various dynamic response analyses and a high-frequency component analysis. The results show that the converter under the PCFF control has a fast dynamic response, ease of control, and a good switching pattern. The theoretical derivation is experimentally verified. >