Pole Shoes Research Articles

Comparative Analysis of Armature Structure on Constant Force Characteristics in Long-Stroke Moving-Iron Proportional Solenoid Actuator

The influence of key design parameters on the constant force characteristics of long-stroke moving-iron proportional solenoid actuators (MPSAs) has been explored by a method combining finite element modelling and correlation analysis. First, the finite element model (FEM) of long-stroke MPSA was developed and validated. Subsequently, the two evaluation indexes, the average-output solenoid force and maximum-output solenoid force variability, were introduced to disclose the influence law of pole shoe parameters on the constant force characteristics of a long-stroke MPSA. After that, correlation analysis was employed to quantify the influence of several parameters and parameter interaction factors on the constant force characteristics. The results indicate a strong contradiction between the average-output solenoid force and maximum-output solenoid force variability; however, increasing the inner diameter of the cone helps enhance the average-output solenoid force without causing maximum-output solenoid force variability to increase. Among all the parameters examined, the cone angle is the most significant parameter affecting the constant force characteristics. Additionally, interactions between the cone angle and the cone length, the cone angle and the inner cone diameter, the cone angle and the outer cone diameter, the cone length and the outer cone diameter, as well as the inner cone diameter and the outer cone diameter also have an important influence on the constant force characteristics. This study deepens our understanding of how the key parameters affect the constant force characteristics and assists designers in optimizing these parameters for developing new structures.

Experiment and Simulation on the Ferrofluid Boundary Deformation and Fluctuation Characters of a High-Speed Rotary Seal

Abstract A ferrofluid seal is a rotary seal widely used in the chemical industry, shipbuilding, aerospace, aviation, and other fields, demonstrating various advantages, such as high reliability, low wear, and low leakage rate. The reason for sealing is that the ferrofluid ring isolates the sealed gas from the atmosphere. Hence, boundary deformation and fluctuation are two significant factors to consider for the design of a ferrofluid seal. However, the ferrofluid boundary is wrapped in the shell and pole shoe, which poses a challenge in direct observation. In this paper, an experimental ferrofluid rotary seal device is presented, which can be used to monitor the boundary changes at different rotational speeds and pressure differences. According to the simulation result, the boundary fluctuation affects the pressure transfer and causes the sealing performance to deteriorate. The ferrofluid boundary obtained through the experiment is essential for an in-depth investigation into the rotary seal failure mechanism for improving the design of the ferrofluid rotary seal.

Design and simulation of a superconducting machine excitation system taking into account the three-dimensional magnetic leakage

The optimized design of a new high-temperature superconducting rotating pole machine is presented. Its main structural feature is the use of a double stator core which separates the synchronous machine pole shoe from the pole body to rotate separately as the machine rotor, allowing the superconducting coil to operate in a stationary state. The inner stator core, the stationary dewar and the rotor core together form the excitation system of the machine. The excitation coil windings adopt a rectangular cross-section, with flux divertor strategically placed between the high-temperature superconducting coils. This configuration aims to modulate the background magnetic field, specifically reducing the perpendicular magnetic field component. This mitigation minimizes the impact of ambient magnetic fields on the superconducting coil’s current carrying capacity, ensuring an optimized magnetic field environment for its operation. Through the integration of these modifications, the technical and economic parameters of the enhanced high-temperature superconducting machine have been significantly improved. The optimization of design, coupled with detailed calculations of the 3D electromagnetic field, was achieved utilizing the commercial software Ansys EM module.

Electromagnetic performance analysis of connected double-modulated axial magnetic gear embedded H-shaped pole shoes for generators

Electromagnetic performance analysis of connected double-modulated axial magnetic gear embedded H-shaped pole shoes for generators

Magnetic fluid flow rate and thermal characteristics of hydraulic turbine spindle magnetic fluid seals

The flow and temperature properties of the magnetic fluid are the primary elements impacting the seal stability in the main shaft magnetic fluid seal of the turbine. This study investigated the eddy current and heat field of the magnetic fluid at the seal gap using a mix of numerical computation and experiment and came to the following conclusions: Under the pole tooth groove and the permanent magnet, the magnetic fluid creates symmetrical vortices in the clearance of the magnetic fluid seal device. Below the pole tooth, the magnetic fluid velocity is minimal and essentially constant. The pole shoe and spindle next to the air side of the magnetic fluid seal device have the lowest temperature, and the device’s core has the greatest temperature.

Design and Simulation study of 40 MW PM Generator for the CRAFT

Design studies of two counter rotating permanent magnet (PM) synchronous generators have been performed. The two 40 MW generators have been designed and compared for the Counter Rotating Axis Floating Turbine (CRAFT) with different air-gap diameters. The generators are modelled with validated full physics finite element method (FEM) which also includes dynamic simulations. The simulations are performed by using an electromagnetic model. The model is described by combined field and circuit equations and is solved in a finite element environment. The stator winding of the generators consists of circular cables and the rotor consists of buried ferrite PM. The generator with smaller air-gap diameter will have lower material costs due to smaller frame but higher due to use of more active materials. A comparison of the counter rotating generators with a traditional direct drive has also been performed by maintaining the same voltage but reducing the rotational speed by half. This shows that a generator with a higher rotational speed will have lower material costs due to smaller dimensions and lower weight. Furthermore, a design variation, to reduce the cogging and harmonic content of the voltage by changing the pole shoe, was analyzed. In conclusions, a 40 MW generator design for the CRAFT has successfully been simulated with a multi-physics-FEM. The advantages of using a counter-rotating generator has been established.

Brushless direct current motors with permanent magnets for marine electric drive systems: state and prospects

The main trends in the development of designs, power semiconductor circuits and control systems of promising valve electromechanical converters — brushless DC motors with permanent magnets for marine electric drive and automation equipment, are discussed in the paper. A variant of their implementation in an adjustable electric drive is presented. The object of the study is a brushless direct current electromechanical system, including a synchronous machine with magnetoelectric excitation, covered by positional feedback through a dependent controlled valve switch, and the subject is structures, the circuit of the power part, control systems, the algorithm of functioning and characteristics. The purpose of the research is to evaluate the operational features, properties and possibilities of introducing brushless direct current motors with permanent magnets as marine electric drive systems of low and medium power. The results of research and development are embodied in experimental industrial samples. A variant with microprocessor control has been developed for marine electric drive systems. The switch is assembled on transistor switches that provide high reliability and enhance the functionality of the control system. The minimum necessary system of logical variables, ensuring the implementation of rational laws of switching and speed control, has been formed. Operational characteristics at various leading angles of switching on the switch valves are presented. The presence of pole shoes at the poles introduces significant features in the patterns of their change. The main advantages and features of the proposed design and circuit solutions are formulated in the conclusions. It is indicated that valve motors with excitation from permanent magnets are the most promising solution in terms of integrating an electromechanical converter into an adjustable marine electric drive of a range of small and medium capacities.Engines of this type are structurally simple and reliable, have rigid natural mechanical characteristics, do not require energy for excitation, have a large overload capacity and high speed in transients. Their distinctive feature is the high specific moment.

Application of hybrid excitation in a DC motor for drive of transport rolls in metallurgical industry

Purpose. To determine the effectiveness of the application of hybrid excitation for DC motors of medium power. Estimate the influence of the location of the permanent magnet of the main pole core on the magnitude of the magnetic flux created by it. Methodology. The classical theory of electric machines, the calculation of the magnetic field by the finite element method and analytical comparison were used to conduct the research. Results. The feasibility of using hybrid excitation for DC motors of medium power has been confirmed. The use of hybrid excitation in an experimental direct current motor made it possible to increase the excitation magnetic flux by 11%. This will make it possible to reduce the current load of the excitation winding, increase the reliability of the motor and reduce electrical losses on the excitation. The optimal location of the permanent magnet, according to the criterion of the maximum magnetic excitation flux, is its location at the main pole shoe along the air gap. Originality. The difference between the conducted research and others is that the condition of the research was to keep the dimensions of its motor, the excitation winding and the interpoles winding unchanged. Practical value. The obtained results will allow the designers of dc motors with hybrid excitation to avoid wrong decisions during further research and development of these motors.

Magnetic Field Analysis for the Permanent Magnet Spherical Motor With SMC Core

This paper presents a permanent magnet spherical motor (PMSM) with soft magnetic composite (SMC) core. The analytical model of the no-load air-gap magnetic field of the PMSM with SMC core is obtained based on the Laplace equation with the boundary conditions. When the SMC core is added to the stator teeth, a cogging effect occurs, which makes the three-dimensional magnetic circuit of the entire spherical surface uneven. When the spherical motor completes multi-degree-of-freedom motion, the air-gap magnetic field is severely distorted. In order to solve the above problems, this paper proposes for the first time the method of adding spherical shaped pole shoes to the stator teeth, which perfectly solves the problem of magnetic field distortion in this paper. The air-gap magnetic field distribution is improved by optimizing the structure of the stator tooth pole shoes. Finally, the static torque measurement platform was built to test the rotation energized output torque. The research results of this paper lay a theoretical foundation for the structural optimization design of the PMSM with SMC core.

Design and analysis of underwater power generation characteristics of deflected double-stator switched reluctance generator

The Deflectable double-stator Switched Reluctance Generator (DSRG) has the advantages of simple structure, small volume and multi-dimensional operation. The DSRG and propeller are combined into the application of underwater power generation. With the help of the deflect ability of the generator, the efficiency is improved. Due to the uncertainty of ocean current direction and the structure of switched reluctance generator, the torque ripple is one of the important factors damaging the underwater generator. In order to effectively suppress the influence of torque ripple caused by generator operation, a method of adding pole shoes on the pole side of outer stator is proposed, so as to reduce the torque ripple. The propulsion structure running at different deflection angles is simulated. The torque and speed obtained before and after pole shoe optimization are input into the propeller model. The pressure and speed characteristics of the corresponding blade structure are simulated to verify the effect of optimization and the effectiveness of the power generation system.

Performance Analysis of rotating pole shoe superconducting machine with dual coils

With the improvement of high temperature superconducting (HTS) materials, HTS machines have shown better competitive advantages in wind power generation and other fields. However, the conventional structure of superconducting machines has led to low reliability of the machines due to the complex structures such as brush and rotating dewar. Based on the analysis of the properties of second-generation high-temperature superconducting strips — YBCO strips, a kind of rotating pole shoe superconducting machine (RPHTSM) with dual HTS coils is proposed in this paper, which avoids the use of brush and rotating dewar used in the conventional HTS machine. The three-dimensional model for magnetic field analysis of the RPHTSM is established and the structure of the RPHTSM is optimized according to the calculation. A two-dimensional simplified model was developed and based on which the output performance of the machine was calculated. By comparing with the conventional HTS machine, it is concluded that the dual-coil RPHTSM has great advantage in reducing the consumption of superconducting strips and the inertia of the rotor.

Electromagnetic design and temperature field analysis of hybrid excitation primary permanent magnet linear motor

Hybrid excitation primary permanent magnet linear motor has the dual advantages of high thrust density of primary permanent magnet linear motor and the flexibility on adjusting the air gap magnetic field of hybrid excitation motor. In this paper, two new 36/4 hybrid excitation primary permanent magnet linear motors with different secondary structures are proposed. Based on the detailed introduction of the motor topology and operation mechanism, the structural parameters are optimized, and the pole arc coefficient of the primary pole shoe and the secondary are finally determined to be 0.4. The secondary is magnetoresistive, and the final thrust adjustment range is about 16.8% under the conditions of optimal armature current and current lead angle. The temperature field of the motor in the magnetizing state is analyzed. The results show that the temperature of the motor decreases gradually from the center to both sides after 7200 s of operation of the new hybrid excitation structure, while the permanent magnet will not be demagnetized permanently. It shows an acceptable reliability.

Design of a 24/16 Outer-Rotor Switched Reluctance Motor with Symmetrical/Asymmetrical Pole Shoes for Performance Improvement

Design of a 24/16 Outer-Rotor Switched Reluctance Motor with Symmetrical/Asymmetrical Pole Shoes for Performance Improvement

Flow-State Identification of Oil-Based Magnetic Fluid Seal Based on Acoustic Emission Technology

At present, most research studies on the changing process of the magnetic fluid seal are analyzed with the pressure signal of each chamber or the magnetic fluid flow photos taken by a camera, which need to change the seal structure. Based on nondestructive acoustic emission technology, a flow-state identification model of the oil-based magnetic fluid seal using the grey wolf optimizer and random forest is proposed in this study. The acoustic emission signal and pressure signal are collected at the same time under static conditions in the two-stage pole shoes oil-based magnetic fluid seal experiment. Through power spectrum analysis of the acoustic emission signal with the aid of pressure signal, the changing process before seal failure is divided into three states: no magnetic fluid flow, the first pole shoe magnetic fluid flow, and two pole shoes magnetic fluid flow together. Then, the time- and frequency-domain features of acoustic emission signal samples are extracted to form feature vectors as inputs, and the flow-state identification model is established based on the grey wolf optimizer and random forest. The experimental results show that the testing accuracy and F1 scores (the index representing the precision and recall at the same weight) of three states are close to or higher than 90%. The effectiveness of oil-based magnetic fluid seal flow-state identification model based on non-destructive acoustic emission technology is proved.

Experimental Study and Simulation on the Seal Pressure of a Ferrofluid Seal Using Radial-Charged Magnets

As one of the most mature applications of ferrofluid, the pole shoes of a ferrofluid seal are easily damaged under the situation of the large radial beating of the main shaft. Meanwhile, due to the small size, the pole teeth commonly used in pole shoes harbor problems such as poor processability and low seal pressure under a large gap. In order to solve the aforementioned problems, we proposed a new structure of the ferrofluid seal that uses a radial-charged ring magnet as the magnetic source. Then, considering that the ring magnets have problems of uneven magnetization and installation difficulties, we used split magnets to take the place of ring magnets and proposed the second new structure. According to the study on the distribution of magnetic field in seal gap axially and circumferentially, we obtained the simulation results of the two new structures’ seal pressure. The results revealed that the new structure of the ferrofluid seal with rectangular magnets can solve the aforementioned problems and exhibited a certain amount of sealing pressure.

Numerical Simulation of AC Loss in the Armature Windings of Two 50 Kw-Class All-HTS Motors With Different Pole Shapes

Achieving low AC-loss armature windings is a key challenge to enable all-HTS motors. Large AC-loss is induced in the HTS armature windings through interaction with the rotating magnetic field generated by the rotor. To reduce the AC loss in the armature windings, it is important to minimize the impact of the rotating magnetic field, especially the component perpendicular to the broad face of REBCO conductors. This work presents two different 1500 rpm, 50 kW all-HTS motor designs with different iron pole shapes: one with pole shoes on the iron core for diverting the magnetic flux around the coil windings, and one without pole shoes. REBCO coated conductors are considered for both the armature and field windings and 2D finite-element models of both designs are built using the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T-A</i> formulation and moving meshes. System-wise analysis of the motor in terms of weight and efficiency is discussed based on the simulated AC loss results. The simulation results show that, at 65 K, flux diverting pole shoes provide a 51% AC loss reduction in the HTS armature windings, without weight penalty or motor power rating reduction. Furthermore, simulation results at 20 K show that the AC loss decreases with decreasing operating temperature due to a decrease in the penetrated field in the HTS windings, which reduces the magnetization loss component.

Analytical modeling of permanent magnet linear eddy current brake using magnetic equivalent circuit method

In order to predict the performance of a permanent magnet linear braking (ECB) with cylindrical structure, an analytical model is established in this paper. The model is based on the magnetic equivalent circuit (MEC) method with the consideration of the often ignored magnetic saturation in pole shoe. The influence of induced eddy current is taken into account by introducing the magnetomotive force (MMF) in the model. To obtain braking force, a simple method for approximating the cross-section of the electric field with mean value method is proposed. The proposed model that can predict the braking force performance of ECB in a wide range of structural dimensions is obtained through referring to a small number of finite element models. A prototype test is carried out. The validity of the proposed method is verified through experiment and FEM. Results show that the braking force predicted by the presented method are in good agreement with experimental results and FEM results under different design parameters. The proposed model can accurately represent the variation trend of braking force and critical speed with design parameters.

Performance Analysis and Optimization of Built-In Permanent Magnet and Salient-Pole Electromagnetic Hybrid Excitation Generators for Vehicles

To solve the problems of the low power density of pure electric excitation generator and nonadjustable magnetic field of pure permanent magnet (PM) generator, a salient-pole hybrid excitation generator (HEG) was proposed in this paper. The designed generator realized coexcitation of two magnetic fields by changing the shape of the pole shoes and embedding the combined-pole PM steels. Compared with other HEGs, it had the advantages of high power density, less excitation loss, and small volume. The paper deduced the analytical expressions of the main magnetic field and armature reaction magnetic field of the HEG and analyzed the armature reaction magnetic circuit, the main influencing parameters, and the influence law of each parameter on the generator output performance to complete the parameter matching of the whole machine. The prototype was trial manufactured and tested with the optimized parameters. The results show that the designed HEG has a low voltage regulation rate, good no-load characteristics, and regulation characteristics. It can ensure the regulated output voltage under rated load conditions and meet the application requirement.

Investigation of the Effects of the Pole Shoe Geometry on the IPM T-LSM Features: Application to Free Piston Engines

The paper is aimed at an analytical approach dedicated to the investigation of the effects of the pole shoe geometry on the no-load flux features of inner permanent magnet tubular-linear synchronous machines (IPM T-LSMs). It considers the most common geometries: (i) rectangular pole shoes, and (ii) trapezoidal pole shoes. The proposed approach combines two analytical models which are the magnetic equivalent circuit (MEC) and the permeance function. First, a basic MEC of an elementary part of the machine is considered to predict a preliminary air gap flux density trapezoidal waveform. Then, the accuracy of the proposed approach is enhanced by the incorporation of a mover permeance function that accounts for the PM spoke-type arrangement. The proposed approach is applied to the investigation of the impact of the mover pole shoe shape on the air gap flux density. The developed pole shoe sizing procedure makes it possible the selection of an IPM T-LSM with an appropriate mover geometry for which an investigation of the no- and on-load features is carried out by finite element analysis. The prototyping of the selected topology enables the experimental validation of the back-EMF and the load characteristic.

Split Structure Design of Magnetic Liquid Sealing Device for High Power Motor

According to the special working conditions of high-power motors, this paper designs a split magnetic liquid sealing device. The material is 316 austenitic stainless steel, which has good mechanical properties. In addition, the material contains Mo element, which has good corrosion resistance and high temperature resistance. It is suitable for use under harsh conditions and meets the special use conditions of high-power motors. In addition, the end cover also adopts a split structure. The design of the pole shoe also adopts a split structure, and a connecting hole is opened on it for the two parts of the split structure to be connected with hexagon socket head screws. The pole piece is a key component in the magnetic liquid sealing device. Its function is to form a magnetic circuit. The material is required to have high permeability and low coercivity.