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Unformatted text preview: 1258 IEEE TRANSACTIONS ON MAGNETICS, VOL. 45, NO. 3, MARCH 2009 An Efficient Field-Circuit Coupling Based on a Temporary Linearization of FE Electrical Machine Models Enno Lange, François Henrotte, and Kay Hameyer Institute of Electrical Machines-RWTH Aachen University, D-52062 Aachen, Germany A field-circuit coupling method is presented, whose basic idea is to extract from the finite-element (FE) model a linearized lumped pa- rameter representation of the electrical machines, to be used in the circuit simulator model of the power electronic supply. The dynamic coupled model of the complete drive obtained this way can be iterated over a limited period of time, with a time step adapted to the high frequency of electronic commutations. When the temporary representation of the machine has come, or is expected to have come under a given accuracy threshold, a new FE simulation is performed, a new set of lumped is generated and the process is repeated. This method allows decoupling the time constants of the field problem from that of the circuit problem, which is typically one or two orders of magnitude smaller. This yields a considerable saving of computation time with a controllable, at least a posteriori , loss of accuracy. Index Terms— Electric machines, energy-based linearization, field-circuit coupling, finite element methods. I. INTRODUCTION V ARIOUS approaches have been developed to simulate electrical machines driven by high frequency power con- verters. Whereas strong coupled approaches, e.g., [1] or [2], suffer from prohibitive computation times, weak coupled ap- proaches, as proposed by [3], allow decoupling the time con- stants of each domain, which may differ by several orders of magnitude, making it possible to establish efficient and accu- rate numerical models. This paper presents a method for coupling efficiently the com- putation time expensive finite-element (FE) model of an elec- trical machine with an external power electronics circuit. It is first explained how a linearized lumped parameter representa- tion of an electrical machine seen from stator terminals can be systematically extracted from the FE model. This linearized rep- resentation is then inserted into the power electronics circuit equations of the converter and the aggregate circuit model is it- erated in time until the linearization error is expected to have be- come too large with suspect to a predefined accuracy threshold. In contrast to [4], the lumped inductance matrix and the elec- tromotive forces are defined here on basis of energy-based arguments. The field problem is thus temporarily represented in the cir- cuit simulator equation by a set of lumped parameters, and time- consuming finite element simulations are used only to update the lumped parameters at a rate much slower than the rate of switching of the electronic components in the supply system....
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This note was uploaded on 06/08/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.

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