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We have developed a dynamic analytical circuit model to simulate the performance of switched reluctance motors (SRMs). Our model expresses flux linkages as multiple decoupled one-argument functions, either current dependent or rotor position dependent, instead of one two-argument function dependent on both current and rotor position. We propose a novel approach for the computation of the air gap permeance at various rotor positions. By using this analytical model, the performance of a SRM can be simulated very efficiently and with improved accuracy. As an application example, we present a simulation of an 8/6 pole SRM in the system domain, and compare the results with transient finite element analysis (FEA) solutions. [ABSTRACT FROM AUTHOR]

Group communication systems are high-availability distributed systems providing reliable and ordered message delivery, as well as a membership service, to group-oriented applications. Many such systems are built using a distributed client-server architecture where a relatively small set of servers provide service to numerous clients. In this work, we show how group communication systems can be enhanced with security services without sacrificing robustness and performance. More specifically, we propose several integrated security architectures for distributed client-server group communication systems. In an integrated architecture, security services are implemented in servers, in contrast to a layered architecture, where the same services are implemented in clients. We discuss performance and accompanying trust issues of each proposed architecture and present experimental results that demonstrate the superior scalability of an integrated architecture. [ABSTRACT FROM PUBLISHER]

We present a general approach to directly couple finite-element models with arbitrary electric circuits for application to electromagnetic devices. We describe both two-dimensional (2-D) and three-dimensional (3-D) transient finite-element models, with emphasis on 3-D using a T-Ω formulation. For 3-D transient and circuit coupling, the derivation of the induced voltage is an integral part of the coupling approach, and the induced voltage links the magnetic field and the electrical circuit together. The system of electric circuits is created automatically. Then graph theory is used to deduce the circuit by tree/cotree and loop analysis. The resulting field equations and circuit equations are coupled together and solved simultaneously at each time step in the time domain. We give three examples of applications: a brushless dc motor drive, a permanent-magnet synchronous motor drive, and a three-phase power transformer with rectifier and load circuit. [ABSTRACT FROM AUTHOR]

We present an approach for directly coupling transient magnetic fields and electric circuits. The circuit can contain arbitrarily connected solid conductors located in the magnetic field region. A systematic procedure suitable for both nodal method and loop method is used to couple fields and circuits. The structures of the system equations of the two methods are analogous. The formulations allow the equations in stranded windings and solid conductors to be unified and the coefficient matrix of the system equations to be symmetrical. In order to reduce the solution domain, the periodic boundary conditions are still applicable when the solid conductors are involved. Our approach has been applied to the simulation of electric machines. We give four examples: 1) calculation of the input phase current and output torque when a single-phase induction motor with shaded rings is in locked-rotor operation; 2) simulation of the sudden short circuit of a synchronous generator with starting cage; 3) study of the phase current waveform of an induction motor when the rotor bars are broken; and 4) investigation of the parasitic capacitive impact of the surge voltage on a winding due to drive switching and cable ring. [ABSTRACT FROM AUTHOR]