442 research outputs found
Magnetic Model Self-Identification for PM Synchronous Machine Drives
The Magnetic Model Self-Identification of PM Synchronous machines is proposed and experimentally validated. Provided that the shaft is free to turn, the commissioning procedure consists of spinning the machine to positive and negative speed values by way of an appropriate pattern of dq current reference values. The flux linkage versus current curves of the machine are constructed during the test via the standard measurements available on any industrial drive: phase currents, dc-link voltage and shaft position. Respect to the literature, the proposed method does not require a specific test rig nor off-line mathematical manipulation
Impact of maximum back-EMF limits on the performance characteristics of interior permanent magnet synchronous machines
Interior permanent magnet (IPM) synchronous machines are vulnerable to uncontrolled generator (UCG) faults at high speed that can damage the inverter. One approach to reducing this risk is to impose limits on the maximum machine back-EMF voltage at top speed. This paper presents the results of a comparative design study that clarifies the nature and extent of the penalties imposed on the IPM machine metrics and performance characteristics as a result of imposing progressively tighter values of back-EMF voltage limits. As an alternative to limiting back-EMF and penalizing machine designs, this paper also investigates the effectiveness of the system-side protection approach to the same UCG fault problem.Seok-hee Han, Thomas M. Jahns, Metin Aydin, Mustafa K. Guven, Wen L. Soon
Design and experimental verification of a 50 kW interior permanent magnet synchronous machine
This paper presents the design details for an IPM machine designed to deliver 50 kW constant power over a 5:1 speed range extending from 850 rpm to 4250 rpm, with a gradual reduction in the required output power up to 8000 rpm (25 kW). Electromagnetic, thermal, and structural considerations have been included in the design optimization process. The resulting machine is designed with two magnet layers per pole and a distributed stator winding. Special features of the machine include its deep stator slots and four-layer winding, made necessary by the desire to minimize the machine's moment of inertia. Test results available to date demonstrate that the machine is capable of delivering the required output torque and power, and the agreement between the predicted and measured machine parameters is generally quite good. Calculated iron losses for high-speed flux-weakening operation are presented in the final section of the paper, illustrating the challenges associated with minimizing the impact of high-frequency harmonic flux density components.Jahns, T.M.; Seok-Hee Han; El-Refaie, A.M.; Jei-Hoon Baek; Aydin, M.; Guven, M.K.; Soong, W.L
Are we close to the QGP? - Hadrochemical vs. microscopic analysis of particle production in ultrarelativistic heavy ion collisions
Ratios of hadronic abundances are analyzed for pp and nucleus-nucleus
collisions at sqrt(s)=20 GeV using the microscopic transport model UrQMD.
Secondary interactions significantly change the primordial hadronic cocktail of
the system. A comparison to data shows a strong dependence on rapidity. Without
assuming thermal and chemical equilibrium, predicted hadron yields and ratios
agree with many of the data, the few observed discrepancies are discussed.Comment: 12 pages, 4 figure
Antiproton Production in Collisions at AGS Energies
Inclusive and semi-inclusive measurements are presented for antiproton
() production in proton-nucleus collisions at the AGS. The inclusive
yields per event increase strongly with increasing beam energy and decrease
slightly with increasing target mass. The yield in 17.5 GeV/c p+Au
collisions decreases with grey track multiplicity, , for ,
consistent with annihilation within the target nucleus. The relationship
between and the number of scatterings of the proton in the nucleus is
used to estimate the annihilation cross section in the nuclear
medium. The resulting cross section is at least a factor of five smaller than
the free annihilation cross section when assuming a small or
negligible formation time. Only with a long formation time can the data be
described with the free annihilation cross section.Comment: 8 pages, 6 figure
Atomic quantum systems in optical micro-structures
We present experiments with cold atoms in optical dipole potentials which are directed towards developing an integrated coherent atom optics with micro-optical systems. We describe an experiment on evaporative cooling in a far-detuned optical dipole trap for âžâ·Rb. The dipole trap is created by a solid state laser at a wavelength of 1030 nm. To achieve high initial phase space densities allowing for efficient evaporative cooling, we have optimised the loading process from a magneto-optical trap into the dipole trap. Starting with an initial phase space density of 2 Ă 10â»âŽ the trap depth was ramped down and temperatures below 200 nK and phase space densities of about 0.2 could be reached. These investigations aim at the creation of an âall-opticalâ BEC based on a simple experimental scheme. As an example for an integrated atom optical system, we present the transport of atoms in a ring-shaped guiding structure, i.e. optical storage ring, for cold atoms which is produced by a micro-fabricated ring lens
Real-time simulation and control systems design by the Response Surface Methodology and designed experiments
This paper examines two cases where the fitting of a model to experimental data makes possible the solution of extremely difficult design and simulation problems. In the first (aerospace) case, designed experiments were conducted on a permanent magnet AC motor which provided the motive power for a flight surface actuator in a more electric aircraft application. The Response Surface Methodology is applied to the measured data to achieve inclusion of the component in a real-time distributed aircraft simulation. In the second (automotive) case, oscillatory acceleration responses are controlled via an electronically actuated (drive by wire) throttle. Designed experiments were conducted on the test vehicle to achieve a systematic excitation of the vehicle driveline. An approximation to the measured data is achieved by the Response Surface Methodology allowing a controller to be designed extremely rapidly
Lambda flow in heavy-ion collisions: the role of final-state interactions
Lambda flow in Ni+Ni collisions at SIS energies is studied in the
relativistic transport model (RVUU 1.0). It is found that for primordial
lambdas the flow is considerably weaker than proton flow. The inclusion of
final-state interactions, especially the propagation of lambdas in mean-field
potential, brings the lambda flow close to that of protons. An accurate
determination of lambda flow in heavy-ion experiments is shown to be very
useful for studying lambda properties in dense matter.Comment: 14 pages, LaTeX, figures available from [email protected], to appear
in Phys. Rev.
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