A Review on Variable Flux Machine Technology: Topologies, Control Strategies and Magnetic Materials

Abstract

Modern applications demand challenging operation requirements from electrical machines. Variable-flux machine (VFM) concepts are found to offer new opportunities for improved machine design. This paper reviews the VFM technology. Three topologies, mainly the parallel hybrid VFMs, series hybrid VFMs, and variable-flux flux intensifying type VFMs are discussed in detail. The variable-flux flux Intensifying machines are found to be the state-of-the-art VFM technology available to-date. The paper also reviews the magnetization process in the VFMs and relates this with the B-H curve of the magnetic material. The conventional PM machine mathematical model is adapted to represent the operation of the VFMs. The different operational limitations of the VFMs are explained and the different modes of operation of the VFMs have been reviewed and compared. The magnetization state manipulation techniques are reviewed. The AC magnetization is found to be the more preferable approach to reduce weight and manufacturing complexity of the VFMs. The trapezoidal current pulse based approach is popular in AC magnetization state manipulation, however, new advanced forms of current vector trajectory control techniques offer comparatively better magnetic state manipulation and higher speed capability for remagnetization of the magnets in the VFMs. The paper also reviews the different magnetization state estimation techniques that are useful during control systems development for the VFMs. The magnetic material for the VFM design is reviewed and potential alternative magnetic material that can satisfy the requirements of the VFMs have been identified. Finally, the current status, challenges, and the potential of VFMs technology are discussed in the conclusion of the paper.INDEX TERMS Variable flux machines, wide speed range, permanent magnet machines, field weakening, magnetic material, magnetization, demagnetization, machine design.

Design and Analysis of a Novel Mechanical Variable Flux Interior Permanent Magnet Synchronous Motor

“…But meanwhile, excessive demagnetization current will cause additional copper loss which will result in lower efficiency [3][4][5]. Therefore, novel topologies and flux-adjusting mechanisms of the VFM have been proposed in recent years, and the VFM not only has the advantages of the traditional permanent magnet (PM) motor but also can effectively adjust its internal magnetic field [6,7]. In the current state of research, Mechanical Variable-Flux Motor (MVFM) [7][8][9][10][11][12][13][14][15][16][17][18] has attracted increasing attention of experts and scholars.…”

Evaluation of Magnetic Behavior of a Single Pole Pair Fe-Cr-Co-Based Memory Motor Considering Standstill Magnetization

“…ARIABLE Flux Memory Machines (VFMM) [1] present as major feature an adjustable air gap flux density. Current pulses are injected in the armature windings along the magnetization axis allowing these machines to operate under dynamically changing load conditions [2], in a wider torquespeed range envelope. Particularly for operations above the base speed, the possibility of using short-time magnetization currents for demagnetizing the low coercive force (LCF) magnet is an advantage.…”

“…This paper is focused on single-type AC-magnetized single pole design composed of a solid cylindrical Fe-Cr-Co-based rotor. A review in VFMM topologies is presented in [2], [10]. The variation of the magnetization level of the magnet is proposed by injecting current pulses in the stator windings at standstill.…”

Design and Analysis of Variable Leakage Flux Flux-Intensifying Motor for Improve Flux-Weakening Ability

“…Permanent magnet synchronous machines (PMSMs) have obvious advantages in high torque density, high power density, and high efficiency [1]. Hence, PMSM has become a research hotspot and widely researched and applied in electric vehicles (EVs) and hybrid electric vehicles (HEVs) [2]. However, the air-gap magnetic field of PMSM is difficult to adjust due to the inherent properties of PM [3].…”