Showing papers by "University of Tabriz published in 1993"

Aspects of design optimisation for switched reluctance motors

Abstract: Existing papers about suitable switched reluctance motor (SRM) airgap dimensions, which give optimum performance for doubly-salient structure motors, are reviewed and their deficiencies are mentioned. The recommendations of these papers cover a wide range of t/ lambda (tooth width/tooth pitch), which can optimise the performance of the SRM. Although some parts of these results are supported by the present work, some other parts may not be correct. A developed software package has been applied to the design of a single-tooth peg stator pole SRM. It is concluded that the optimum ratio of t/ lambda is between 0.33 and 0.40. Using the design constraints considered, the optimum split ratios (defined as the ratio of rotor diameter to stator outer core diameter) are estimated at between 0.57 and 0.63. The ratio between the back of core width and half of tooth width in the motor is estimated and it is found that the best range of this ratio is from 1.1 to 1.3. >

The group of automorphisms of non-associative commutative algebras associated with the group of automorphisms of 2-designs

Abstract: 1. Introduction. Let f2 be a finite set with I f21 = v, and ~ is a collection of b subsets of f2, each of cardinality k; that is, I~[ = b and IBI = k for all B ~ ~. The pair D = (f2, N) is called a 2-design if each pair of distinct elements of f2 occurs in exactly one element of +~. Elements of ~ and ~ are called points and blocks, respectively. It is proved that each point occurs in the same, call r, blocks. The constants v, b, k and r are called the parameters of D and it is proved that they satisfy in the following relations: bk = vr, r(k - 1) = v- 1.

Optimum design of three phase induction motor based on efficiency optimisation

Abstract: The nonlinear optimisation method of Hooke-Jeeves, in which partial derivatives are not required, has been employed for optimum design of the three phase induction motor. The method is capable of producing an optimum design which meets or exceeds all constraints and performance specifications. The results obtained by this technique is fully comparable with a more complicated optimisation technique such as the Han-Powell method. The optimisation method was able to approach the optimum operating point, satisfying the imposed constraints and achieving a stable optimum design. The optimum design was achieved with 117 iterations and 290 seconds computation time on PC/AT. >

A nonsinusoidal reference wave for PWM AC drives

Abstract: The authors propose a suitable reference wave for pulse width modulation (PWM) AC Drives. Staircase reference waves whose levels are calculated to eliminate certain harmonics, are studied. A certain staircase reference waveform with L levels is constructed; when L is made very large, in limit, this staircase waveform approaches a continuous one which is called Quasine (Quasi+Sine). This approach compared to the classical harmonic elimination method has the advantage that the magnitude of nontriplen harmonics is reduced. The authors developed a computer program by TURBO PASCAL 6 to have a comparison between the harmonic contents of output voltage for various reference waveforms. >

Teaching aids for electrical machines laboratory

Abstract: A personal computer software package has been recently developed in the electrical machines laboratory at Tabriz University. The package includes a set of computer programs that can be used alongside experiments, to assist students in learning the experimental aspects of electric machines.

Two-photon transitions in the optogalvanic spectrum of neon

Abstract: Seventeen two-photon transitions for neon have been observed in the 580-635 nm spectral regionfor use in the spectroscopic study of its higher excited levels, which are not accessible by one-photonabsorption. To compare the two and one-photon absorption signals being originated from the some lowerlevel, an effort was made to record single-photon optogalvanic spectrum in the available wavelengh region. The dependence of optogalvanic signal on the laser power has also been studied. The optogalvanic signals were obtained from a commerical neon-filled hollow-cathode lamp, which wasirradiated with pulsed dye laser pumped with N2 laser. 1. INTRODUCTION Two-photon absorption is the simultaneous absorption of two photons by a molecule which undergoes a transition E1->Ef with (Ef-E1) = h(w1 +w2). The photons may either come from a single laserbeam passing through the absorbing sample or they may be provided by two beams emitted from one ortwo lasers. The first detailed theoretical treatment of two-photon processes was given in 1931 by

Performance criteria for gas turbine cogeneration plant

Abstract: With current gas turbine practice up to two-thirds of the energy available in the fuel is lost in the form of unused heat, By making practical use of this waste heat in a recovery boiler to produce steam for district heating or process applications it is possible to reduce the energy wastage to as little as 10 percentIn this paper different performance criteria for assessment of a gas turbine cogeneration plant (GTCP) have been defined and compared with each other, Also, the practical range of performance criteria have been determinedCopyright © 1993 by ASME