Computation of load performance and other parameters of extra highspeed modified Lundell alternators from 3D-FE magnetic field solutions

A combined magnetic vector potential, magnetic scalar potential method of computation of 3-D magnetic fields by finite elements, in combination with state modeling in the abc frame of reference, is used for global 3-D magnetic field analysis and machine performance computation under rated load and overload condition in an example 14.3 kVA modified Lundell alternator. The results vividly demonstrate the 3-D nature of the magnetic field in such machines and show how this model can be used as an excellent tool for computation of flux density distributions, armature current and voltage waveform profiles, and harmonic contents, as well as for computation of torque profiles and ripples. Use of the model in gaining insight into locations of regions in the magnetic circuit with heavy degrees of saturation is demonstrated. Experimental results which correlate well with the simulations of the load case are given     

Three dimensional magnetic field computation by a coupledvector-scalar potential method in brushless DC motors with skewedpermanent magnet mounts-the formulation and FE grids

A three dimensional finite element (3D-FE) method for the computation of global distributions of 3D magnetic fields in electric machines containing permanent magnets is presented. The formulation of this 3D-FE method including 3D permanent magnet modeling, which is based on a coupled magnetic vector potential-magnetic scalar potential (CMVP-MSP) approach, is given. The development of the necessary 3D-FE grids and algorithms for the application of the method to an example brushless DC motor, whose field is three dimensional due to the skewed permanent magnet mounts on its rotor, is also given here. A complete set of results of application of the method to the computation of the global 3D field distributions and associated motor parameters under no-load and load conditions are detailed in a companion paper     

Nonlinear Vector Potential Formulation and Experimental Verification of Newton-Raphson Solution of Three Dimensional Magnetostatic Fields in Electrical Devices

An iterative technique, based on magnetic vector potential formulation and the Newton-Raphson method, for the determination of the three dimensional magnetostatic field distributions in electrical devices is given. The proper degrees of magnetic saturation in the various materials within a given volume under consideration are obtained by repeated evaluation of the reluctivities in that volume, using a cubic spline representation of the B-H magnetization characteristics of composite materials (laminations). The formulation has been applied to a practical example of determining the field in and around a shell type 1.5 kva single phase transformer. The convergence and implementation characteristics of the developed method are given in this paper which show a saving of about 34% in CPU solution time in comparison with previously published methods. Experimental verification is given in terms of a comparison between computed and experimentally obtained values of flux densities surrounding the transformer core and winding, under heavily saturated conditions. Excellent agreement between test and calculated flux densities was achieved. This method is thus quite applicable to the solution of a wide class of three dimensional magnetostatic field problems associated with electrical apparatus.     

Comparison between characterization and diagnosis of brokenbars/end-ring connectors and airgap eccentricities of induction motorsin ASDs using a coupled finite element-state space method

This paper describes how a rigorous and comprehensive time-stepping coupled finite element-state space (TSCPE-SS) modeling technique can be utilized in diagnostics and differentiation between induction motor rotor (cage) abnormalities of broken bars/connectors and airgap eccentricities. The model is used for the computation of time-domain performance characteristics, such as the stator phase current waveforms and developed torque profiles including these abnormalities. This is followed by analysis of the current waveforms and torque profiles using fast Fourier transform to obtain their corresponding frequency spectra. Comparison between the TSCFE-SS model's simulation results, which correlate very well with theoretical results, clearly illustrate that rotor bar and/or end-ring connector breakages can be distinguished from static and dynamic airgap eccentricities. This paper also gives an interesting comparison between the effects and implications of these various rotor abnormalities on machine parameters and performance characteristics. Furthermore, the results indicate that frequency components reported earlier to be produced only by the combined effects of static and dynamic airgap eccentricity could be observed in case of either static or dynamic eccentricity. Finally, this paper demonstrates the possible opportunities that can be made use of in noninvasive detection of airgap eccentricities via TSCFE-SS and current signature techniques     

Pathways through which glucose induces a rise in [Ca2+]i of polymorphonuclear leukocytes of rats

Basal levels of [Ca2+]i are elevated in diabetes mellitus. Such an abnormality is most likely due to both increased calcium influx into cells and decreased efflux of this ion out of the cells. The present study examined the cellular pathways that are responsible for hyperglycemia-induced acute rise in polymorphonuclear leukocytes (PMNL), and explored whether such a rise is due to increased calcium entry into PMNL and/or to calcium release from their intracellular stores. There were dose dependent and time dependent rises in the [Ca2+]i of PMNL exposed to high concentrations of glucose. Similar effects were observed when the PMNL were exposed to high concentrations of choline chloride or mannitol. A substantial part of the rise in [Ca2+]i was inhibited when the media contained verapamil or nifedipine or when the PMNL were placed in calcium free media, and the rise in [Ca2+]i was completely abolished when the PMNL were placed in calcium free media containing ryanodine. GDP beta S or pertussis toxin almost completely prevented the glucose-induced rise in [Ca2+]i of PMNL. Rp-cAMP, H-89 or staurosporine produced significant inhibition of the rise in [Ca2+]i. High concentrations of glucose produced a dose dependent shrinkage of PMNL volume over a period of two hours. The volume of PMNL, however, was normal after 24 hours in vitro incubation studies as well as after 1, 2 and 12 days of streptozotocin-induced hyperglycemia in rats. The results are consistent with the formulation that the osmotic activity (cell shrinkage) of the high glucose concentrations activates G protein(s) which then stimulates the adenylate-cAMP-protein kinase A pathway, phospholipase C system and calcium channels. The stimulation of these cellular pathways permits both calcium influx into the PMNL as well as mobilization of calcium from their intracellular stores. Both of these events contribute to the acute rise in their [Ca2+]i. It is possible that the rise in [Ca2+]i is critical for the stimulation of the events that lead to the generation and accumulation of inorganic osmolytes to restore cell volume to normal.     

Mathematical model: Retention of beryllium on flow-through fixed bed reactor of Amb-IR-120

A mathematical model was proposed to simulate the beryllium uptake within a fixed porous flow-through reactor. The effects of various structural, kinetic and hydraulic parameters on the behavior of the flow reactor were studied. These include linear velocity of the fluid, packing density, void fraction and adsorption coefficient. The proposed mathematical model is solved analytically and its predictions were compared with experimental results. A reasonable agreement between model predictions and experimental data was obtained. The model is approved to simulate the behavior of beryllium uptake along the fixed bed reactor of Amb-IR-120 and can be easily applied to similar systems.     

Modeling and experimental verification of the performance of a skewmounted permanent magnet brushless DC motor drive with parameterscomputed from 3D-FE magnetic field solutions

This paper contains a comparison between actual laboratory-measured performance of a brushless DC motor drive system, with skewed permanent magnet mounts on its rotor, and two computer-simulated motor drive system performance characteristics. These simulated motor drive system performance results were once obtained using motor parameters computed from rigorous three dimensional-finite element (3D-FE) magnetic field solutions detailed in two companion papers and once obtained using motor parameters from more conventional 2D-FE magnetic field solutions. The comparison demonstrates that 3D-FE based motor parameters lead to drive system performance simulations which are much closer to test results for this type of brushless DC drives with skewed permanent magnet mounts. Torque ripples computed from 3D-FE based and 2D-FE based motor parameters are also included. The results clearly show advantages to basing the drive system simulations on 3D-FE computed motor parameters     

Three dimensional magnetic fields in extra high speed modifiedLundell alternators computed by a combined vector-scalar magneticpotential finite element method

A three-dimensional (3-D) finite-element (FE) approach was developed and implemented for computation of global magnetic fields in a 14.3 kVA modified Lundell alternator. The essence of the method is the combined use of magnetic vector and scalar potential formulations in 3-D FEs. This approach makes it practical, using state-of-the-art supercomputer resources, to globally analyze magnetic fields and operating performances of rotating machines which have 3-D magnetic flux patterns. The 3-D FE computed fields and machine inductances as well as various machine performance simulations of the 14.3-kVA machine are presented     

Extra high speed modified Lundell alternator parameters andopen/short-circuit characteristics from global 3-D-FE magnetic fieldsolutions

A combined magnetic vector potential, magnetic scalar potential method of computation of 3-D magnetic fields by finite elements is used for global 3-D field analysis and machine performance computations under open-circuit and short-circuit conditions for an example 14.3 kVA modified Lundell alternator, whose magnetic field is of an intrinsic 3-D nature. The computed voltages and currents under these machine test conditions were verified and found to be in very good agreement with corresponding test data. Results of the use of this modeling and computation method in the study of a design alteration example, in which the stator stack length of the example alternator is stretched in order to increase voltage and volt-ampere rating, are given. These results demonstrate the inadequacy of conventional 2-D based design concepts and the need for this type of 3-D magnetic field modeling in the design and investigation of such machines     

Transient Analysis of Partial Armature Short Circuit in an Electronically Commutated Permanent Magnet Motor System using an Integrated Nonlinear Magnetic Field-Network Model

The simulation of the dynamic performance characteristics of an electronically commutated brushless dc machine system with radially oriented permanent magnets, which is experiencing a partial short in one of its phases, is reported in this paper. The newly introduced integrated field network (IFN) method was used throughout this work. The IFN method, which is detailed in a companion paper, is based on simultaneously solving the dynamic equations of the machine system network, using machine winding parameters (inductances and emfs) which are determined from numerical solutions of the nonlinear magnetic field prevailing in the machine cores for the corresponding winding currents. These field solutions and corresponding machine parameters are updated at every time step of the solution of the dynamic equations. The results presented here document effects of the shorting of a portion of an armature phase winding on the dynamic performance of a 15 hp (11.2 kw), 120 volts samarium-cobalt permanent magnet brushless dc motor. A comparison of the current, inductance, enf, torque and power time profiles of the motor system with and without partial armature winding failure (short) is given here. These studies are of importance in motor system security and redundancy considerations. The dramatic change of the values of machine parameters upon occurrence of the partial short circuits demonstrate that conventional solution methods would have left much to be desired.