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This paper presents a finite element analysis (FEA) based method for analyzing and controlling the bias magnetic state of the transformer of a pulse-width-modulation (PWM) switching full bridge dc-dc converter. A field-circuit indirect coupling method for predicting the transient bias magnetic state is introduced first. To increase flexibility of the proposed method, a novel transformer model which can address not only its basic input-output characteristic, but also the nonlinear magnetizing inductance, is proposed. Both the asymmetric characteristic and the variable laws of the current flowing through the two secondary windings during the period of PWM switching-off state are highlighted. Finally, the peak magnetizing current controlled method based on the on-line magnetizing current computation is introduced. Analysis results show that this method can address the magnetic saturation at winding ends, and hence many previous difficulties, such as the start-up process and asymmetry of power electronics, can be easily controlled. [ABSTRACT FROM AUTHOR]

An electromagnetic design of a double-sided high temperature superconducting (HTS) linear synchronous motor (HTSLSM) with an HTS bulk magnet secondary is introduced in this paper. A HTS magnetic suspension system is applied to replace the sliding rail to levitate the secondary mover resulting in the HTSLSM moving without sliding friction. The thrust model of the HTSLSM is built using a magnetic circuit method and the thrust characteristics obtained from the model are compared with finite element analysis and practical testing results. The theoretical analysis on the prototype has also been verified by measurements. [ABSTRACT FROM AUTHOR]