Search

In order to relieve the problem of bearing wear in high-speed permanent magnet generator, a semi-symmetrical double winding structure with the same number of poles is proposed in this paper. The coupling of the winding magnetic fields enables the rotor to be subjected to a radial electromagnetic force along the direction of overcome gravity, which could effectively extend the service life of the bearings. Firstly, the design principle of the semi-symmetrical double winding structure and the winding MMF are analyzed based on the AC machine winding theory, and the elliptical magnetic field characteristics of the harmonic winding are clarified. Combining the characteristics of order and frequency for harmonic magnetic field, the magnetic fields coupling mechanism of the double winding is revealed, and the analytic model of the power generation and radial electromagnetic force are determined. Secondly, based on rolling contact fatigue theory, the service life improvement of bearing by the double winding structure is certificated. In addition, the magnetic fields of double winding are decoupling calculated by using the finite element method, and the consistency of results between the theoretical analyses and the finite element calculations is determined. Finally, the calculation accuracy of the finite element analysis is demonstrated by experiments on the prototype. [ABSTRACT FROM AUTHOR]

This paper offers a novel dual-mode double stator wound rotor synchronous machine for variable speed applications. The proposed motor integrates the benefits of both the traditional wound rotor synchronous machine (WRSM) and brushless wound rotor synchronous machine (BL-WRSM). A constant torque can be attained in the maximum torque per ampere region by operating the proposed machine as a traditional WRSM in Mode I, and a constant power can be attained in the field-weakening region by operating it as a BL-WRSM in Mode II. Moreover, due to the dual-stator structure, the proposed machine exhibits improved performance in terms of high torque density as compared to the existing single stator BL-WRSM. By using a special stator winding arrangement to achieve the sub-harmonic component of the stator magnetomotive force, the brushless operation of the proposed machine is achieved. The additional sub-harmonic component induces a voltage in the harmonic winding placed on the rotor, which is then rectified and provided a DC current to field winding for brushless excitation. In order to validate the effectiveness of the proposed machine, a two-dimensional finite element analysis (FEA) is carried out. [ABSTRACT FROM AUTHOR]

This article introduces a hybrid consequent-pole brushless wound rotor synchronous machine (CP-BL-WRSM). The CP-BL-WRSM installs permanent magnets (PMs) on the alternative rotor poles. Compared with the conventional BL-WRSM and permanent magnet-assisted brushless WRSM (PM-BL-WRSM), the proposed machine provides advantages of high average output torque, high maximum torque, and high starting torque. In addition, the proposed CP-BL-WRSM’s torque ripple is also lower than the conventional brushless WRSM. The volume of PM in the CP-BL-WRSM machine is lower than the conventional permanent magnet synchronous machines (PMSMs) and PM-BL-WRSM. In this brushless topology, the machine uses three-phase stator windings powered by a single inverter, which provides a unique armature current to the stator windings that comprises of fundamental and third-harmonic components. The fundamental current component is used to generate the main stator field, and the third-harmonic current component is used to induce a harmonic current in the harmonic winding. A diode rectifier installed on the rotor is used to rectify the harmonic current. After the rectification, a direct current (DC) is injected into the field winding of the rotor to form a rotor magnetic field and achieve brushless operation. In order to verify the operation of the proposed CP-BL-WRSM topology and analyze its performance, 2-D finite element analysis (FEA) was used in JMAG-Designer. Finally, the performance of the proposed CP-BL-WRSM topology was compared with the conventional BL-WRSM topology and PM-BL-WRSM topology to verify its higher starting torque, higher average torque, and higher maximum torque and higher minimum torque. The proposed topology can replace the existing highly expensive PM synchronous machines (PMSMs) due to its less PM volume and conventional BL-WRSMs due to its better performance.

This paper offers a novel dual-mode double stator wound rotor synchronous machine for variable speed applications. The proposed motor integrates the benefits of both the traditional wound rotor synchronous machine (WRSM) and brushless wound rotor synchronous machine (BL-WRSM). A constant torque can be attained in the maximum torque per ampere region by operating the proposed machine as a traditional WRSM in Mode I, and a constant power can be attained in the field-weakening region by operating it as a BL-WRSM in Mode II. Moreover, due to the dual-stator structure, the proposed machine exhibits improved performance in terms of high torque density as compared to the existing single stator BL-WRSM. By using a special stator winding arrangement to achieve the sub-harmonic component of the stator magnetomotive force, the brushless operation of the proposed machine is achieved. The additional sub-harmonic component induces a voltage in the harmonic winding placed on the rotor, which is then rectified and provided a DC current to field winding for brushless excitation. In order to validate the effectiveness of the proposed machine, a two-dimensional finite element analysis (FEA) is carried out.

This paper presents a novel dual-mode wound rotor synchronous machine (DWRSM) for variable speed applications. The proposed machine combines the advantages of both the conventional wound rotor synchronous machine (CWRSM) and the brushless wound rotor synchronous machine (BWRSM). Unlike the existing BWRSM, through the dual-mode operation of the proposed machine, constant torque is achieved in the constant torque region by operating the machine in mode-I, i.e., as a CWRSM, and constant power is achieved in the field weakening region by operating the machine in mode-II, i.e., as a BWRSM. The mode change is performed through an additional thyristor drive circuit. The airgap magnetomotive force (MMF) in both modes is derived analytically. To verify this principle, finite element analysis (FEA) and an experiment on a 1- horsepower prototype machine was performed, and key influential factors were verified. The transients in the stator currents and torque during the mode change was analyzed. The test results validated the correctness of the theory and the FEA results.

This paper proposes a permanent magnet assisted brushless wound rotor synchronous machine (PMa–BL–WRSM) design. The proposed machine has the advantage of a high starting torque compared to existing BL–WRSM topologies. Additionally, the average torque increases and the torque ripple is reduced when the permanent magnet assisted machine structure is used. PMa–BL–WRSM operates on the principle of brushless excitation using zero-sequence, third-harmonic current generation in the stator windings. The third harmonic component is harnessed to induce a voltage in the harmonic winding which is mounted on the rotor. As there is no flux generated from filed winding in the starting, the starting torque of the machine is also zero. To overcome the problem, permanent magnets (PMs) are inserted in each field tooth to provide the initial source of flux on the rotor. Finite element analysis is performed with the PM–BL–WRSM, and the elicited results are compared with the basic machine structure. The proposed machine operation is verified using 2-D finite element analyses using the ANSYS Maxwell analysis tool. [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]

This paper proposes an inverter scheme to generate an additional third-harmonic component alongside the fundamental component of the current. The generated third-harmonic component is used to achieve the brushless operation in a wound field synchronous machine (WFSM). Contrary to the traditional schemes used, i.e., dual inverter, single inverter with extra switches schemes, and single inverter with four transistor legs, the proposed scheme comprises a single inverter with three transistor legs that utilizes a modified third-harmonic injection pulse-width modulation. The brushless operation in WFSM requires two windings on the rotor periphery, i.e., harmonic winding and field winding that are interconnected through a rotating diode bridge rectifier. To maximize the usage of generated third-harmonic component, the selection of pole–slot combinations of the machine is carried out considering the winding factors. The proposed inverter scheme is verified in MATLAB, and a 2-D finite element analysis is used to validate the brushless operation of the machine along with its electromagnetic performance. [ABSTRACT FROM AUTHOR]

This paper presents a novel consequent-pole hybrid brushless wound-rotor synchronous machine (CPH-BL-WRSM). The proposed machine employs permanent magnets (PMs) on the alternate poles of the salient pole rotor, which has considerably less magnet usage compared to the regular (PM) assisted synchronous machine. The proposed CPH-BL-WRSM offered the advantages of high starting torque, high torque density, and better performance under full-load conditions. The BL operation for the proposed machine is achieved by generating a composite magneto motive force (MMF) with a fundamental component and sub-harmonic component. The sub-harmonic component of the stator MMF is used for BL excitation of the rotor. The finite-element method was used to analyze the performance of the CPH-BL-WRSM in comparison with the performance of the existing BL-WRSM and regular PM-assisted BL-WRSM. Finally, a prototype of the CPH-BL-WRSM was manufactured and the experiment was conducted to demonstrate the performance of the proposed CPH-BL-WRSM. [ABSTRACT FROM AUTHOR]

This paper proposes a new topology for a brushless wound rotor synchronous machine (BL-WRSM) using a specially designed stator winding supplied through a single three-phase inverter. In this topology, a special stator winding, which comprises of two sets of series-connected windings with an unequal number of turns, is used to generate an additional spatial sub-harmonic component in the stator magneto-motive force (MMF). This additional sub-harmonic MMF (SH-MMF) component is utilized for exciting the field winding of the BL-WRSM. The advantage of the proposed brushless topology is the use of a single inverter compared to a dual inverter used in the existing dual inverter BL-WRSM. For the rotor, there are two separate windings: (1) harmonic winding and (2) field winding. Both the harmonic and field windings are connected in parallel with each other through a rotating rectifier. The additional SH-MMF component generates a rotating air-gap magnetic field, which induces the voltage in the harmonic winding. This induced voltage is then rectified and used to supply a dc current to the field winding. A 2-D finite element analysis is performed to analyze and verify the operating principle of this new BL-WRSM. [ABSTRACT FROM AUTHOR]

This paper presents an optimal design of a recently introduced brushless wound-rotor synchronous machine (BL-WRSM). The BL-WRSM, with a special stator winding arrangement, utilizes a single three-phase inverter for generating an additional spatial subharmonic component in the stator magnetomotive force (MMF). This subharmonic component of the stator MMF is used for the brushless excitation of the rotor. The pole span and pole shoe height were the optimized parameters, with the goals of improving the quality of output power and reducing torque ripple. Moreover, the average torque of the machine was improved by optimizing the harmonic winding placed on the rotor. The optimized BL-WRSM was further analyzed for the flux weakening operation. Finite element analysis (FEA) was carried out to analyze the performance of the BL-WRSM. Finally, the performance of the optimal BL-WRSM model was verified through an experimental test, which demonstrated good agreement with the simulation results. [ABSTRACT FROM AUTHOR]