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A new harmonic field excitation technique for the brushless operation of wound field synchronous machines (WFSMs) is proposed in this paper. The proposed scheme involves conventional three-phase and single-phase inverters operating at different frequencies and supply input current to the armature winding simultaneously. This results in a composite output current of the inverters, which contains fundamental as well as the third harmonic current components. The fundamental is utilized to develop the stator field, on the other hand, the third harmonic is used for developing the pulsating magnetomotive force (MMF) in the airgap. This MMF produces a harmonic current in the harmonic winding of the rotor which is later rectified to inject field current to the rotor field winding. The theoretical analysis of the proposed technique is supported using 2-D finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

This manuscript discusses a novel harmonic current excitation technique for a wound rotor synchronous machine based on control of the time harmonic magneto-motive force (MMF) for brushless operation. Two inverters are used to feed the armature winding in such a way that at a time, one inverter supplies the current to armature winding. The two inverters are 180° phase-shifted. The inverter assignment is based on time-division multiplexing technique to generate continuous armature currents containing reasonable third-harmonic component beside fundamental component. This third-harmonic current component generates pulsating MMF and is induced in the rotor harmonic winding; the induced current is rectified and applied to rotor field winding to generate rotor field. The rotor field interacts with armature fundamental current component for torque generation. Finite element analysis is performed to verify the idea. [ABSTRACT FROM AUTHOR]

Numerous industrial facilities involve the installation of load transformers with their respective loads. As these loads are engaged and disengaged, their transformers are also energized and de-energized, respectively. An inrush current, which typically occurs when a transformer is energized, can easily be observed for an online uninterruptible power supply (UPS) system feeding such loads. This paper proposes an online UPS system that eliminates the inrush current phenomenon caused by the switching-in of the load transformers. The UPS inverter specifically utilizes a fast acting current control scheme which enables it to regulate the load current during all energizing conditions of the load transformer connected to the UPS system. Experimental results are provided to validate the effectiveness of the proposed UPS system. [ABSTRACT FROM PUBLISHER]

This paper presents a new high-efficient three-phase brushless wound rotor synchronous machine (BL-WRSM) based on a sub-harmonic field excitation technique. In the proposed machine topology, the stator is equipped with two different three-phase windings: (1) main armature winding, and (2) additional armature winding. The main armature winding is based on a 4-pole winding configuration, whereas the additional armature winding is based on a 2-pole winding configuration. Both windings are supplied current from two different inverters, i.e., inverter-1, inverter-2, and simultaneously. Inverter-1 provides the regular input current to the main armature winding, whereas inverter-2 provides a three-phase current of low magnitude to the 2-pole additional armature winding. This generates an additional sub-harmonic component of MMF in the airgap beside the fundamental MMF. On the other side, the rotor is equipped with (1) harmonic, and (2) field windings. These windings are electrically coupled via a rectifier. The fundamental component of MMF produces the main rotating magnetic field, whereas the sub-harmonic MMF gets induced in the harmonic winding to produce harmonic current. This current is rectified to give DC to the rotor field winding to attain brushless operation. To authenticate the operation and analyze its performance, the proposed BL-WRSM topology is supported using 2-D finite element analysis (FEA) in JMAG-Designer. Later on, the performance of the proposed brushless topology is compared with the customary BL-WRSM topology to verify its high efficiency, high output torque, low torque ripple, and low unbalanced radial force on the rotor. [ABSTRACT FROM AUTHOR]

In an open-winding machine, three-phase stator currents can be controlled such that the input armature currents may contain the third-harmonic current component in addition to the fundamental. Considering this attribute of open-winding patterns, a harmonic current field excitation technique for a wound rotor synchronous machine (WRSM) is proposed in this paper based on the control of time-harmonic magneto-motive force. Two inverters connected to both terminals of the stator winding are controlled so that the input armature current generates an additional third-harmonic current component. This third-harmonic component generates a vibrating magnetic field that induces a current in the specially designed rotor harmonic winding. The current is supplied as DC current to the rotor excitation winding to generate a rotor field by using a full-bridge diode rectifier in order to achieve brushless operation. The proposed dual-inverter-controlled brushless operation for a WRSM is executed in ANSYS Maxwell using 2-D finite element analysis to validate its operation and electromagnetic performance. [ABSTRACT FROM AUTHOR]