Salient Permanent Magnet Machine Research Articles

Theoretical analysis of AC current supply of doubly salient permanent magnet machine with quasi sinusoidal back-EMF and inductance variations

Theoretical analysis of AC current supply of doubly salient permanent magnet machine with quasi sinusoidal back-EMF and inductance variations

Torque characteristic improvement of dual-PM modular doubly salient permanent magnet machine using machine ratio adaptation

Machine ratio adaptation of a dual-PM modular doubly salient permanent magnet machine (DPM-DSPM) was proposed to improve the torque characteristics. An optimization design process was examined. Essential machine indicators were investigated to obtain an optimal machine ratio. It was found that p = 4 and a 0.8 rotor pole width ratio of the DPM-DSPM produced the best essential machine indicator that provided the appropriate magnetic flux path and high flux regulation quality. Then, the DPM-DSPM with an optimal machine ratio was investigated based on open-circuit and on-load tests and then compared to a reviewed DPM-DSPM. The results, based on 2-D finite element analysis, verified that the optimal proposed DPM-DSPM had better torque characteristics. In particular, the optimal proposed structure produced 35.04% higher electromagnetic torque with 61.75% lower ripple torque than the review structure. Therefore, an optimal machine ratio for a DPM-DSPM can be beneficial in solving industrial machine problems, especially noise reduction from vibration.

Development and Performance Comparison of Single-Stator and Dual-Stator Doubly Salient Permanent Magnet Machines

Development and Performance Comparison of Single-Stator and Dual-Stator Doubly Salient Permanent Magnet Machines

A Novel Slot-PM Assisted Complementary-Rotor Doubly Salient Machine With Enhanced Torque Performance

This article presents a novel doubly salient permanent magnet (DSPM) machine with enhanced torque performance. The key is that an assistive magnetic flux is produced by using two sets of slot PMs inserted into the slot openings, which can effectively improve the torque production. Besides, a complementary magnetic path is built by dual rotors with 180° angle shift to reduce leakage flux, which can effectively suppress the torque ripple. In this article, the proposed machine design is presented, including working principle, winding configuration, magnetic path analysis. Then, the Genetic Algorithm is used to find the optimal designs for the proposed machine. Further, to verify the effectiveness of the proposed machine, three doubly salient machines are compared, including the proposed machine, a DSPM machine without assistive slot PM design, and a dual-rotor DSPM machine without complementary rotor structure. Finally, a prototype of the proposed machine is built and tested to verify the validity of the proposed machine design.

Comparative Study of Biased Flux PM Machines Having Different Stator Core Segments and Armature Winding Configurations

This article proposes a comparative study of biased flux permanent magnet (BFPM) machines having different stator core segments and armature winding configurations. The topologies of the four investigated machines and their operating principles are introduced first. Then, in the case of same envelope size and copper loss, all four BFPM machines are designed based on the single variable optimization method to obtain higher average torque, along with their comparison of electromagnetic characteristics such as phase back-electromotive force (back EMF), cogging torque, and torque capability. It is shown that by exploiting both flux focusing (FC) and dual armature (DA) design, the average torque of the BFPM machine has a 132% sharp increase. Furthermore, to reveal the real performance of the DA-FC-BFPM machine, its comparison with machines such as DA doubly salient permanent magnet (DA-DSPM) machine, DA flux reversal permanent magnet (DA-FRPM) machine, DA flux switching permanent magnet (DA-FSPM) machine, wound rotor synchronous (WRS) machine, and surface-mounted permanent magnet (SPM) machine is performed. Finally, a prototype machine is built and tested to verify the finite-element predictions.

Design of Doubly Salient Permanent Magnet Generator for Output Power Enhancement using Structural Modification

The doubly salient permanent magnet generator (DSPMG) is widely known as an efficient machine for electrical production from renewable energy. In this paper, we aim to improve the output power of the DSPMG using a structural modification, which is targeted for low-speed electrical generations. Structural parameters including the stator pole depth, thickness of permanent magnet, stator pole arc, and number of winding turns were adjusted, then an optimal value of those parameters was selected based on the characteristics of the generator tested during no-load and on-load conditions. Simulations were based on the finite element method. The generator was targeted to be used for the rated power of 200 W. It was found that the optimally designed generator had a higher electromotive force of 36.1%, a lower cogging torque of 20%, and a higher output power of 12.2% than the conventional structure. The leakage flux of the proposed structure was also improved from the conventional one. Thus, the generator designed in this work could be another capable choice for electrical generation from renewable energy. The proposedly modified technique can also be adapted for output profile improvement of the doubly salient permanent magnet machines which are extensively used for renewable energy production nowadays.

Electromagnetic Performance Comparison of Doubly Salient PM Machines With Different Stator Iron Core Segments

This article compares the electromagnetic performances of doubly salient permanent magnet (DSPM) machines with different stator iron core segments. Since the permanent magnets (PMs) of the DSPM machines studied in this article exist in pairs, the feasible numbers of PMs in the 12/8-pole DSPM machine are 12, 6, 4, and 2, and thus, the corresponding stator tooth number between two adjacent PMs is 1, 2, 3, and 6, respectively. Therefore, the stator iron core segments of the four DSPM machines have different shapes. Furthermore, to improve the average torque, PMs are inserted into the slots, and flux focusing teeth are adopted. All four machines are designed to achieve larger average torque under the fixed copper loss and envelope size. The comparison shows that the DSPM machine with two stator teeth between adjacent PMs exhibits the largest average torque and the smallest torque ripple. Moreover, the DSPM machine with six stator teeth between two adjacent PMs has the optimal PM utilization. To verify the predicted results, a 12/8-pole DSPM prototype with two stator teeth between adjacent PMs is manufactured and tested.

Comparative Study of Novel Doubly Fed Doubly Salient PM Machines With Different Stator/Rotor-Pole Number Combinations

This article presents a novel doubly fed doubly salient permanent magnet machine (DFDSPMM) with armature windings wound around stator and rotor teeth. Compared with the conventional doubly salient permanent magnet machine (DSPMM), this machine locates an extra winding in the rotor slots as armature winding to fully use its rotor slot space, thus leading to an increase in the output torque. The structure and operational principle of the proposed machine are analyzed at first. Then, the feasible stator/rotor-pole number combinations are discussed. Furthermore, the electromagnetic characteristics of the investigated machines are predicted based on the 2-D finite element (FE) analysis. It shows that higher torque density and lower cogging torque can be achieved by the proposed DFDSPMMs with improved stator/rotor-pole number combinations. Moreover, the proposed DFDSPMMs are compared against a surface-mounted permanent magnet machine (SPMM) to reveal comprehensive performance. Finally, the prototype is built and tested to validate the 2-D FE predictions.

Comparative Study Between Doubly Salient PM Machine With New Stator/Rotor-Pole Number Combination and Biased Flux PM Machine

This article compares the doubly salient permanent magnet machine (DSPMM) having 18/13-pole number combination with 18/17-pole biased flux permanent magnet machine (BFPMM) to verify its improvement in torque characteristics. In such DSPMM, the stator/rotor-pole number combination is 18/13 rather than the conventional one (i.e., 18/12) to achieve balanced three phases, sinusoidal phase flux linkage and back electromotive force (back EMF), small cogging torque, and low torque ripple. On the other hand, an 18/17-pole BFPMM having the similar structure with the 18/13-pole DSPMM is analyzed, which has the best torque performance among such machines with the same stator pole number. To further improve average torque, the inner-type flux focusing (IFC) method is employed in both 18/13-pole DSPMM and 18/17-pole BFPMM. Then, both machines are optimized under the fixed copper loss and envelope size. The comparison shows that both machines have comparably small torque ripple while the 18/13-pole DSPMM with IFC (IFC-DSPMM) exhibits 35% higher torque density and 100% higher ratio of torque to PM volume. An 18/13-pole IFC-DSPMM is manufactured and tested to experimentally validate the predicted results.

Improved Stator/Rotor-Pole Number Combinations for Torque Ripple Reduction in Doubly Salient PM Machines

Doubly salient permanent magnet (DSPM) machines suffer from a large torque ripple due to unbalanced three phases, nonsinusoidal-phase back electromotive force, large cogging torque, etc. To suppress the torque ripple, this article proposes a new type of stator/rotor-pole number combinations. The number of stator poles is 18, while the number of rotor poles differs from the conventional counterpart (i.e., 12) by one. The DSPM machines with different stator/rotor-pole number combinations are globally optimized under the fixed copper loss and machine envelope. It shows that compared with the 18/12 stator/rotor-pole DSPM machine, the torque ripples of 18/11 and 18/13 stator/rotor-pole DSPM machines are reduced significantly, while their torque densities remain almost the same. An 18/13 stator/rotor-pole DSPM machine is built and tested so as to experimentally verify such improvement.

An Improvement of Output Power in Doubly Salient Permanent Magnet Generator Using Pole Configuration Adjustment

The doubly salient permanent magnet (DSPM) machines are very attractive for low-speed power generation. In this work, we propose a design technique to improve the output power of the DSPM generator by an adjustment of pole configuration. The number of stator and rotor poles, split ratio, as well as the stator pole arc of the generator, were proposedly adjusted and optimized. The output characteristics of the generator including the magnetic flux linkage, electromotive force, harmonic, cogging torque, electromagnetic torque, output voltage and output power were analyzed through finite element analysis. The symmetrical magnetic field distribution of all generators was firstly verified. Then, the results indicated that this particular generator was optimized at 18 stator poles and 12 rotor poles, while the split ratio and the stator pole arc should be set as 0.78 and 6.15 degrees, respectively. The proposed optimal generator could provide a significant improvement in the output voltage and the output power compared to the conventional structure. The output power of 1.28 kW can be reached by the optimal structure, which was two times higher than that of the conventional structure. The physical explanation regarding to the structural modification was also given. The proposed design technique can be applied for improving the output power of the DSPM machines.

High-order sliding mode control of a doubly salient permanent magnet machine driving marine current turbine

Due to the harsh and changeable marine environment, one low speed stator-permanent magnet machine named doubly salient permanent magnet machine with toothed pole is applied for marine current energy conversion system. Indeed, this machine has simple structure, intriguing fault tolerance, and higher power density, which could adequately satisfy the different complicated operation conditions. However, its permanent magnet flux-linkage has the same variation period as the inductance which leads to a strong nonlinear coupling system. Moreover, the torque ripple caused by this special characteristics, uncertainty of system parameters and disturbance of load greatly increases the difficulty of control in this strongly coupling system. Consequently, the classical linear PI controller is difficult to meet the system requirement. In this paper, the high-order sliding mode control strategy based on the super-twisting algorithm for this system is creatively utilized for the first time. The stability of the system within a limited time is also proved with a quadratic Lyapunov function. The relative simulation results demonstrate convincingly that, the high-order sliding mode control has little chattering, high control accuracy and strong robustness.

No-Load Performance Analysis of an Asymmetric-Pole Single-Phase Doubly Salient Permanent Magnet Machine

Asymmetric-pole single-phase doubly salient permanent magnet machine (APSP-DSPMM) can yield higher torque and lower dead zone than the traditional one. Some special structural factors, such as the stator pole pieces, unequal air-gap lengths, and seriously saturated auxiliary teeth, if not properly considered, may bring large errors in the electromagnetic performance evaluation. This article proposes an improved magnetomotive force-specific permeance method to account for these special structural factors. This method is implemented numerically to obtain the electromagnetic performance of APSP-DSPMM under the conditions of no-load and full-load, and the results are compared with those of the two-dimensional finite-element analysis. The theoretical results are verified by the experimental test results of a prototype.

Design and Analysis of a Hybridly Excited Asymmetric Stator Pole Doubly Salient Machine

This article presents the design and analysis of a 12/7 (numbers of stator/rotor poles) hybridly excited asymmetric stator pole doubly salient machine (HEASPDSM) with a main focus on the special topology and operational principle by using the analytical and 2-D finite element analysis. A full comparison is conducted on the average torque, torque ripples, no-load back electromotive force and flux regulation capacity under the condition of different structural parameters, which can provide good references to the machine design. A 12/7 HEASPDSM is designed and the main performance indexes are analyzed in detail. Based on the parameters, the performance of 12/7 HEASPDSM is compared with traditional 6/7 doubly salient permanent magnet machine (DSPMM) with the same volume and thermal load. Finally, a prototype of the 12/7 HEASPDSM is manufactured and tested to validate the theoretical analysis. The results fully demonstrate that the HEASPDSM possesses the merits of strong flux regulation capability, higher torque density, and wider constant power speed range benefitted from the dc field winding than the traditional DSPMM.

Equivalent Magnetic Circuit Analysis of Doubly Salient PM Machine With Π-Shaped Stator Iron Core Segments

An equivalent magnetic circuit (EMC) analytical method for a 3-phase doubly salient permanent magnet (DSPM) machine with Π-shaped stator iron core segments (Π-core DSPM machine) is presented in this paper. This method is based on the airgap field modulation theory. First, the airgap permeance of the doubly salient machine is calculated, based on which the influence of slotting on modulation effect is analyzed. Then, an EMC model of this machine is established according to its main magnetic field distribution. Considering the slotting effect on the average airgap flux density, Carter's coefficient is used to calculate the equivalent airgap length and the airgap magnetomotive force (MMF). Subsequently, the flux density is calculated, which allows the calculation of no-load electromotive force (EMF) and also on-load torque. In addition, the relationship between machine performances and key dimensions can be obtained by analytical expressions without complicated finite element analysis (FEA). Analytical results are validated by both the 2-dimension FEA and experimental results.

Design and Simulation of Two Phase Doubly Salient Permanent Magnet Machine with a Dual Stator Structure

A new type of doubly salient permanent magnet machine with a dual stator structure is proposed. The motor is designed by staggering two stators by 45°on a 4/6 pole structure of double-salient pole motor. The motor has the advantages of high power density, small pulsation and high efficiency. The basic structure and working principle of the motor are introduced. The air-gap flux is calculated by the simple magnetic circuit method. The no-load magnetic field distribution, air gap flux density and permanent magnet Flux, back EMF, inductance characteristics of the machine are analyzed by using finite element simulation software. The inherent cogging torque of permanent magnet machine is analyzed. The simulation results verify the rationality of the new structure machine.

One special current waveform of toothed pole doubly salient permanent magnet machine for marine current energy conversion system

Marine current energy becomes more and more attractive because of its remarkable advantages. In this paper, one toothed pole doubly salient permanent magnet (DSPM) machine is proposed for marine current energy conversion system. This kind of machine has a simple structure, good fault tolerance, reliable operation, and high power density, which make it very suitable for marine tidal current applications. However, DSPM machine is conventionally operated by means of current chopping control and angle position control in a different region due to the trapezoidal back electromotive force (EMF) waveform. While for this toothed pole DSPM machine, the PM flux-linkage, inductance, and back EMF have more sinusoidal waveforms, which make the sinusoidal current be possible. Unfortunately, the classic sinusoidal current generates a relatively large torque ripple owing to the special inductance. Consequently, the primary purpose of this paper was to design one special current waveform to further reduce the torque ripple. Firstly, the model of the toothed pole DSPM machine is presented. Secondly, the torque distribution theory is proposed without taking into account mutual inductance effect. The mathematic expressions of the currents are deduced subsequently. Thirdly, several fitting currents are analyzed and compared based on the theoretical currents. Moreover, the simulation results verify the torque distribution theory and allow proposing the optimal current waveform (fundamental and second harmonic) in comprehensive consideration of the voltage, powers, and torque ripple. Finally, some robustness analysis is also presented to show the good performances of this current.

A Novel Structure of Doubly Salient Permanent Magnet Machine in Square Envelope

In conventional 12/8-pole doubly salient permanent magnet machines (DSPMMs) with outer type flux focusing method, the relatively thicker stator back iron next to magnets results in smaller slot area. This paper proposes a novel structure of DSPMMs in square envelope. In such structure, the thickness of stator back iron is roughly uniform and the magnets are inserted from the corners of square envelope to the slots. In addition, the tooth tips of all stator teeth are kept uniformly distributed on the stator bore while the tooth bodies of side stator teeth next to magnets are bended by an angle from the corresponding tooth tips. Meanwhile, the side stator teeth size should be optimized to achieve the balanced slot areas. The main parameters of the proposed and conventional structures with outer type flux focusing method are scanned for higher torque under the fixed copper loss and square envelope. The comparison between two structures shows that the proposed structure can achieve larger slot area, lower torque ripple, and 11.5% higher average torque with the same magnet usage.

Kynurenic acid analogue SZR-72, but not SZR-73, SZR-81 and SZR-104 treatment moderates the severity of acute necrotizing pancreatitis in rats

This paper presents the impact results of the variation of the rotor and the stator tooth pitches (Vernier effect), on the waveform of the back-electromotive force (EMF) generated by the low speed Doubly Salient Permanent Magnet machine (DSPM). The rotating electrical machines with and without Vernier effect are designed and optimized using genetic algorithms combined with finite element method. The optimization of machines parameters is focused on the maximization of the mass to torque ratio. The results show that the machine with Vernier effect has better performances. The obtained Vernier slotted doubly salient permanent magnet generator is then integrated into an autonomous wind energy conversion system. Simulations tests are carried out through Matlab/Simulink. The results show that the proposed machine is a valid and inexpensive alternative for directly coupled wind turbines.

Flux concentrated doubly salient linear permanent magnet machine

Different topologies of Vernier permanent magnet (PM) machines have been proposed for direct drive low-speed applications due to their high thrust and power density. However, this type of machine can suffer from low power factor (PF). In this study, a flux concentrated doubly salient linear permanent magnet machine with V-shape PM arrays is proposed and compared to a consequent pole (CP) type machine. Using the configuration of V-shaped PMs allows the flux to be concentrated in iron spacers located between two pieces of PMs. This feature is shown to result in an improvement of the airgap flux density, which allows a reduction in electrical loading and hence an improvement in power factor. In order to achieve a fair comparison, two doubly salient linear permanent magnet machines with different PMs’ configurations have been analysed and compared using transient FEA. The investigated machines have the same overall machine and, crucially, magnet volume. The results confirm that the proposed V-shape machine is capable of higher thrust force, higher no-load back EMF and can achieve a higher PF of 42% compared to the consequent pole machine, while it consumes the same amount of the PM material.