Influence Of Permanent Magnets Research Articles

Irreversible Demagnetization of a Large Capacity Line-Start Permanent Magnet Synchronous Motors considering Influence of Permanent Magnet Temperature

This paper investigates the irreversible demagnetization (ID) of a large capacity line-start permanent magnet synchronous motor (LSPMSM) considering influence of permanent magnets’ (PMs) temperature. The phenomenon of ID occurs on the pull-in stage and close to the cusp of magnet on the direct-axis direction. The PMs’ temperature causes the demagnetization curve to move down and the knee point to shift up. The extensive area ID of magnet will lead to pulling in synchronism failure and operation at the asynchronous state. A prototype is fabricated to validate the analysis that temperature of PMs will bring more serious ID risk and degradation of motor performance.

Simplified 3-D Hybrid Analytical Modelling of Magnet Temperature Distribution for Surface-mounted PMSM With Segmented Magnets

In this article, a simplified three-dimensional (3-D) hybrid analytical thermal model for surface-mounted permanent magnet (PM) synchronous machines is proposed and applied to investigate the influence of PM segmenting strategies on the spatial PM temperature distributions and hotspots. The developed 3-D hybrid thermal model synergies the lumped-parameter thermal model and analytical method and is able to estimate 3-D spatial temperature distributions and hotspots for both unsegmented and segmented surface-mounted PMs accounting for the uneven PM eddy current loss distributions. Meanwhile, by utilizing the proposed matrix-based post-processing methods, the developed hybrid analytical thermal model has a simple mathematical expression but persists in high estimation accuracy. Finally, the proposed hybrid analytical modelling method is validated by 3-D electromagnetic-thermal coupled FEA and experiments.

A Turn Fault Mitigation Strategy Based on Current Injection Technique for a Triple Three-Phase PMA SynRM

A turn-to-turn short-circuit fault usually causes excessive fault current because of very low impedance associated with a few fault turns. It should be dealt with promptly to avoid further damages to the machine, especially for a permanent magnet (PM) machine. In order to limit the turn fault current, a novel turn fault mitigation strategy based on current injection technique for a triple redundant 3 × 3-phase PM synchronous reluctance machine (PMA SynRM) is investigated in this paper. First, the flux linkage of the fault phase where the fault turns are located is estimated considering the influence of PM and currents in the healthy and fault three-phase sets. This flux linkage, including that of the fault turns, is subsequently reduced by injecting specific currents to the fault three-phase set, leading to much smaller fault current. The proposed current injection method does not affect the operation of the healthy three-phase sets that continue to produce torque. The effectiveness of the proposed method is validated by extensive finite-element (FE) simulation and experimental tests on a prototype 3 × 3-phase fault-tolerant PMA SynRM drive.

Influence of PM- and Armature Winding-Stator Positions on Electromagnetic Performance of Novel Partitioned Stator Permanent Magnet Machines

Since the permanent magnets (PMs) and armature windings of partitioned stator (PS) PM machines are located in two separate inner and outer stators, their positions can be exchanged to optimize the space utilization, especially in radial field rotating machines. Therefore, in this paper, the influence of PM and armature winding stator positions on the electromagnetic performance of PS-PM machines is investigated based on the novel PS-PM machines (PS-PMMs) with surface-mounted PM (SPM) stator. Similar to the single-stator surface-mounted PMMs (SS-PMMs), flexible rotor pole number, bipolar phase flux linkage, and symmetrical phase back electromotive force (EMF) are also obtained in PS-PMMs. Based on the same 12/10 stator/rotor pole number combination, PS-PMM-I (PMs located in the inner stator) and PS-PMM-II (PMs located in the outer stator) exhibit 120% and 160% higher phase back EMFs as well as 120% and 139% larger average torques, respectively, than the SS-PMM together almost without scarifying the PM utilization efficiency under the same machine size and the same rated copper loss. Further, the proposed PS-PMM-IIs have both higher phase back EMFs and larger average torques than PS-PMM-Is among all the main stator/rotor pole number combinations. Meanwhile, for both PS-PMM-Is and PS-PMM-IIs with 12-pole stator, the machines with the 11-pole rotor exhibit the optimal torque capabilities. Moreover, the reluctance torque is also negligible in the proposed PS-PMMs due to very low saliency ratio. The analyses are validated by experiment results of the prototype machine.

A Fully Coupled Framework of Predicting the Dynamic Characteristics of Permanent Magnet Contactor

A fully coupled simulation framework is developed to predict the dynamic characteristics of the permanent magnet (PM) contactors. Dynamic inductance, magnetic field distribution, and mechanical motion are solved by coupling the electric, magnetic, and mechanical governing equations. The equations are developed in the weak forms and the Weak Form Partial Differential Equation module of Comsol Multiphysics is employed to solve the equations. Influence of PM is taken into account by considering the remanent flux as a static potential. The electromagnetic variables and mechanical variables can be solved in the same discrete time period, which gives much higher calculation efficiency than the existing method. The simulation results show that the framework can predict the changing of the inductance, closing displacement, and excitation current in the time domain. Comparative experiments have been conducted to verify the simulations. Physical measurements show that the dynamic closing process of the contactor can be captured by the model with good precisions.

A Novel Bridge-Type Hybrid Saturated-Core Fault Current Limiter Based on Permanent Magnets

To reduce the requirement of dc-coil-generated magnetomotive force, this paper analyzes the method of using permanent magnets (PMs) to saturate the core. In this paper, a novel bridge-type hybrid saturated-core fault current limiter (BHFCL) is proposed to investigate the influence of PM. For the BHFCL, a bridge structure is designed to guarantee the fault clipping performance, with a fault limiting reactor. In addition, the compact structure of magnetic device and the shared coil of alternating current and dc could reduce cost and losses. To compare the influence of PMs on the performance of BHFCL and to validate the effectiveness of the proposed BHFCL, various FEA simulation models in a simple system are carried out by ANSOFT. The simulation results demonstrate that the BHFCL could achieve considerable energy consumption reduction with little effect on the normal condition voltage drop as well as the fault clipping ability. The BHFCL is efficient in fault clipping, and the performance is shown to depend mainly on the value of the reactor included in the bridge.

Numerical analysis of magnetic nanoparticle transport in microfluidic systems under the influence of permanent magnets

A finite element technique was employed for analysing the transport behaviour of magnetic nanoparticles (MNPs) under the gradient magnetic field generated by rectangular permanent magnets with different configurations. To predict the exact particle dynamic behaviour, the governing non-linear differential equations, Navier–Stokes and convection–diffusion were coupled with the magnetic field equation. The MNP concentration distribution was calculated and taken as an evaluation parameter to show where MNPs are preferentially captured in a microchannel. Since the dynamic behaviour of MNPs in the flow was dependent on the competition between magnetic and fluidic forces, the effects of the flow velocity and magnetic field strength on the MNP concentration distribution were analysed. Meanwhile, the effects of magnetic design parameters for permanent magnets on the magnetic force and MNP concentration distribution were analysed. Results showed that the MNP concentration in the capture region increased with magnetic field strength and decreased with increasing flow velocity. And the shape and position of the high concentration regions were related to the applied inlet velocity, magnetic field strength, geometry of the magnets and the orientation of the remanent flux density. The simulations performed can be used as a tool for the design and optimization of millimetre-sized rectangular magnets for developing efficient lab-on-a-chip systems.

Influence of Magnetic Field on Reduction Chatter and of Surface Roughness in End Milling of Titanium Alloy - Ti-6Al-4V

One of the most challenging issues in machining process is understanding the chatter phenomenon. Chatter mechanics is still not fully understood. It is inconsistent in character, making it difficult to analyze and predict. This research work investigates the influence of permanent magnets on chatter suppression in end milling of Titanium alloy (Ti-6Al-4V) using uncoated WC-Co insert. The experiments were designed based on the Response Surface Methodology (RSM) approach using DESIGN EXPERT (DOE) software. The experiments were performed under two different conditions: under normal condition and under the application of magnetic fields from two permanent magnets located in opposite direction. Ti-6Al-4V was used as the work material. The resultant average surface roughness was found to be reduced by a maximum of 50% due to magnet application. Scanning Electron Microscope (SEM) was used to analyze the chip morphology. The microphotographs showed the evidence of more stable chip formation under the influence of magnetic fields.

Influence of Permanent Magnet on the Association Constants of FeCl3+10% PVA (Polyvinylalcohol) in 50% Ethanol-Water Solutions Conductometrically at 298.15K: Using New Equation for 1:3 Asymmetric Electrolytes

The external poles of a permanent magnet of power 1.26 kG were used to study their effect on the conductance values of FeCl3 plus 10% by weight , PVA (polyvinylalcohol) in 50 % by weight mixed ethanol-water solutions. A new equation for 1:3 asymmetric association constant was derived and used for calculating the association constants (KA) for FeCl3 solutions in 50 % ethanol (EtOH)-H2O mixture in presence of PVA and also in absence and presence of an external magnetic field. The new equation was derived from the Fuoss-Shedlovsky equation and Ostwald dilution law and the evaluated values are discussed.

A novel multifunctional rotary actuator with magnetorheological fluid

In some environments with very limited working space, an integrated actuation device with multiple functions would be desirable. This paper is aimed at developing a novel magnetorheological (MR) fluid based multifunctional rotary actuator. To decrease the dimension of the actuation device while enhancing the functionality, a motor part and MR fluid are integrated into one device. With MR fluid, the actuator possesses multiple functions as motor, clutch, and brake. In this paper, the configurations and design details of the motor part and clutch/brake part are illustrated, and the operating principle of the actuator is discussed as well. The torques of the motor part and clutch/brake part are derived. The finite element method is utilized to analyze the magnetic circuits, the influence of permanent magnets on the MR fluid, and the magnetic flux distribution. A prototype of the actuator is fabricated and each function is tested. The results show that the developed actuator is promising for applications which require multiple functions with compact size.

Influence of the Permanent Magnet Magnetization Length on the Performance of a Tubular Transverse Flux Permanent Magnet Linear Machine Used for Electromagnetic Launch

This paper investigates the underlying influence of permanent magnet (PM) magnetization length on the performance of a tubular transverse flux PM linear machine working as the propeller of an electromagnetic launcher, including its main flux linkage, cogging force, and thrust force. The theoretical analysis is brought forward and verified with 3-D numerical computations. It is shown that the cogging force increases with the increase of the PM magnetization length, whereas the main flux linkage and thrust force do not follow this rule, which is quite different from that in conventional PM machines.

Influence of Permanent Magnet on the Association Constants of FeCl3 in 50 % Ethanol−H2O Solutions (Conductometrically) at 298.15 K Using a New Equation for 1:3 Asymmetric Electrolytes

The external two poles of a permanent magnet of a power of 1.26 kG were used to study their effect on the conductance values of FeCl3 in a 50 % by weight mixed ethanol−H2O solvent. The results were compared with values in the absence of the magnet. A new equation for the 1:3 asymmetric association was obtained and used for the calculation of the association constants (KA) for FeCl3 solutions in a 50 % ethanol (EtOH)−H2O solvent in the absence and presence of an external magnetic field. The new equation was derived from the Fuoss−Shedlovsky equation and Ostwald dilution law, and the evaluated values are discussed.

High speed motor supported by active magnetic bearings with high nonlinearity

In a high speed motor system supported by active magnetic bearings,the influence of permanent magnets in the motor rotor and the residual unbalance in the rotor is obvious. The active magnetic bearings have to work in nonlinearity and high speed running is hard to be achieved.To deal with the marked nonlinearity in the active magnetic bearing system,an exact linearization method is used to linearize the magnetic forces of the active magnetic bearings.Meanwhile,controller designs are improved.A gain schedule method is used to make the rotor running stable across its rigid critical speed.Through adding a zero-pole pair to a PD controller,the gain of the controller in the frequency domain near the running frequency of the rotor is effectively decreased and the rotor runs almost about its mass center.Then the saturation of the magnetic forces in the active magnetic bearings is avoided and stable running of the motor system at high rotation speeds is achieved with high nonlinearity in the active magnetic bearings.

Influence of permanent magnets on vibration characteristics of a partially covered sandwich cantilever beam

The shear strains of viscoelastic damping layers resulting from the attraction arrangement magnets on the constraining layers root are higher than those of the conventional passive constrained layer damping treatment (PCLD). Therefore, significant improvement of damping characteristics can be achieved by using the new class of magnetic constrained layer damping treatment (MCLD). This paper presents an analytical modelling to elucidate vibration attenuation mechanism of the MCLD. It is shown that the variation amplitude of viscoelastic damping layers shear angle at the root where permanent magnets are fitted is relatively high, producing relatively high dynamic magnetic force compared to the maximal force on the constraining layers. The dynamic magnetic force is strong enough to reduce the elastic potential energy of the constraining layers and the primary layer and enhances the dissipation energy of the damping layers. The rise in the ratio of the dissipation energy to the total system energy per cycle suppresses the resonance peak. Furthermore, influences of permanent magnets on resonance peaks for the first several modes under different physical and geometrical properties are evaluated. Such evaluations are used to determine the merits and limitations of the MCLD treatment and develop design guidelines.