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This paper investigates the torque production and the torque ripple reduction of 6-stator/7-rotor-pole (6/7) variable flux reluctance machine (VFRM). Based on the harmonic analysis, the instantaneous torque equation is firstly derived by considering the spectra of the armature inductance and current. The average torque is found to be mainly produced by the mutual inductances between the field and...
This paper proposes a novel reluctance axis shifted (RAS) machine with hybrid rotors, i.e., permanent magnet (PM) and synchronous reluctance parts, respectively. The proposed design is geometrically characterized by two axially parallel rotors, which enables the full utilization of reluctance and magnet torque components for torque improvement. In the proposed design, the reluctance axis coincides...
This paper proposes a novel flux-reversal hybrid magnet memory machine (FR-HMMM), which is geometrically characterized by consequent-pole hybrid magnets mounted on the stator poles. The low-coercive-force (LCF) permanent magnets (PMs) are alternately placed between the adjacent stator slots, while the rare-earth NdFeB PMs are located on the center of stator pole. Due to the consequent pole configuration,...
In this paper, the stator/rotor pole combinations in variable flux reluctance machines (VFRMs) are investigated from the prospect of magnetic gearing effect. Firstly, the magnetic gearing effect in the torque production of VFRMs is revealed from an analytical model. Based on this, the principles of feasible stator/rotor pole selection and corresponding winding configuration are analyzed. Then, the...
Two permanent magnet linear machines, i.e. partitioned stator flux reversal permanent magnet (PS-FRPM) and conventional switched flux permanent magnet (SFPM) linear machines, are compared, in terms of electromagnetic performance and demagnetization withstand capability. It is found that compared to the conventional SFPM linear machine, the PS-FRPM linear machine shows lower cogging force, higher thrust...
Partitioned stator flux reversal permanent magnet (PS-FRPM) linear machine is a type of permanent magnet linear machine with dual active stators and one passive mover. Pervious work was shown that such a machine possesses the advantage of having big slot area leading to reduced phase resistance and consequently improved electric loading capability. In order to verify the finite element (FE) results,...
Hybrid permanent magnet (PM) variable flux memory (VFM) machines employ both the high coercive force PM, i.e. the constant PM (CPM), and the low coercive force PM, i.e. the variable PM (VPM), with which the PM magnetization state can be flexibly regulated to match various operation requirements. These two kinds of PMs can be magnetically connected with either parallel or series configuration so that...
This paper proposes a novel variable reluctance hybrid magnet memory machine (VR-HMMM), which is geometrically characterized by doubly salient structure having homopolar hybrid magnets alternatively mounted on the stator poles. The magnetizing coils are wound on the PM excitation teeth to vary the magnetization states of low coercive force (LCF) magnets, and hence the air-gap flux can be flexibly...
The unbalanced magnetic force (UMF) occurs in permanent magnet (PM) machines when there is rotor eccentricity. This paper investigates the influence of slot/pole combination and magnet thickness on UMF in PM machines having different rotor eccentricities and magnetizations. It shows the machines with different magnetizations have different UMFs due to rotor eccentricity when magnet thickness and slot/pole...
In this paper, more than ten different iron loss models are experimentally evaluated, which covers alternating and rotating fields, influence of temperature, DC bias flux density and distorted flux density due to PWM inverter. Iron loss models considering alternating fields are evaluated by the measured results of a lamination ring specimen. The iron loss model considering rotating field and nonsinusoidal...
This paper investigates the influence of stator slot/pole number combinations on the rotor bar current waveform and electromagnetic performance of a squirrel-cage induction machines (IMs) designed with a slot number per pole per phase of two. 36-slot/6-pole (36S6P), 48S8P, and 60S10P IMs, all having 52 rotor slots, have been designed by using the same winding layout, stator outer diameter, stack length,...
The effect of number of rotor slots on the stator and rotor current waveforms, slot and tooth flux densities and performance characteristics, such as torque, torque ripple, losses, electromagnetic force, power factor, and efficiency are numerically studied in case of a 3-phase, 8-pole squirrel-cage induction machine (IM). The IMs have been designed by using the same winding layout, stator outer diameter,...
In this paper, the torque production mechanisms of integral slot distributed, fractional slot concentrated winding (FSCW) and Vernier permanent magnet synchronous machines (PMSMs) are firstly investigated together from the perspective of magnetic gearing effect. The torque contribution and magnetic gearing effect in eight 12-slot PMSMs with different rotor pole numbers are analysed and compared. The...
In this paper, an 18-slot/26-pole fractional slot permanent magnet surface-mounted machine (FSPMSM) with coil-pitch of 2 slot-pitches is firstly proposed. The torque production of this machine is based on both the principle of fractional slot machine and magnetic gearing effect. Its performance is analysed and compared with that of an 18-slot/10-pole FSPMSM. The results show that the 18-slot/26-pole...
Permanent magnet vernier machines are receiving more and more attentions in low-speed high-torque applications due to their inherent features such as compact structure, high torque density, low torque ripple, etc. This paper presents and compares several linear topologies of permanent magnet vernier machines, all of which have double-sided secondary and toroidal-winding configuration. By using finite...
This paper proposes a phase correction strategy for the zero sequence back EMF based sensorless drive under current regulation control (viz., I/f control). The straightforward phase correction process based on the nearest principle might lead to false correction under different load conditions. The proposed strategy can achieve robust phase correction by injecting transitory high frequency (HF) signal...
In this paper, the influence of magnet thickness on the electromagnetic performance of high speed machines is comprehensively investigated. The investigation is carried out based on a conventional 3-slot/2-pole high speed machine with diametric magnetization. Both the finite element method (FEM) and analytical models are used. The rated output torque is fixed when the magnet thickness varies. It is...
The performance evaluation of an adjustable space-vector (SV) PWM (SVPWM) strategy for open-winding (OW) permanent magnet synchronous machine (PMSM) (OW-PMSM) drives with common DC bus is presented. Different from modifying the conventional SVPWM algorithm, the proposed method is realized by reconstructing the voltage references for individual SVPWM module. No need of modification on a conventional...
This paper presents a partitioned stator (PS) switched flux permanent magnet (PS-SFPM) synchronous generator (PS-SFPM-SG) and its electromagnetic characteristics under different load conditions. The adopted PS structure enables the PS-SFPM-SG to achieve higher power and torque density due to enlarged slot space for the armature windings by moving PMs to an inner stator. Hence, the space conflict between...
High speed machines have received much attention recently. However, unbalanced magnetic force (UMF) may occur in some slot/pole number combinations even there is no rotor eccentricity, which can cause high vibration and noise. In order to reduce the rated on-load UMF, three 3-slot/2-pole permanent magnet (PM) machines with different auxiliary slots are investigated and compared in this paper. In the...
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