Back Yoke Research Articles

Studying the quality indicators of acrylic paints with suede effect decorated in youth clothing

The article provides a comparative analysis of the types of national patterns in the formation and decoration of modern youth clothing. In the preparation of modern youth clothing, the structure and use of “tórt qulaq,” “qus qanaty,” and “óńirjıek” ornaments among the national ornaments of the Kazakh people were substantiated. According to the analysis results, the study used the methods of artistic decoration of national elements with volumetric acrylic paints, decorating with an artistic painting of ornaments of a collection of modern youth clothing formed. We studied the influence of dyeing textile materials of mixed composition with acrylic paints and the quality indicators of test samples decoratively decorated with acrylic paints on textile materials. When decoratively finishing brushed “poker with fleece” fabric with “Decola” acrylic paint, applying the paint to the test sample created difficulties. As a result, we discovered that the paint did not lie smoothly on the fabric’s surface. Test samples of the “milana” suit fabric and raincoat material using “Pebeo acrylic paint with suede effect” acquired a 3D volume. We studied the color fastness of washing test samples, and high-quality indicators of color fastness with artistic ornamental finishing in 3D volumes were obtained for the material “raincoat” and the suiting fabric “milana.” When studying the performance of test samples in terms of hygroscopic properties, the raincoat material had a higher waterproof rating, and the “milana” suit fabric had a lower waterproof rating. As a result of the hygroscopic properties of materials, in the manufacture of a collection of youth clothing, “milana” suit fabric was used, and the decorative detail of the “back yoke” was made of raincoat material with a high waterproof rating. As a result of the study, the ornaments will be decorated with artistic painting with “Pebeo acrylic paint suede effect” with 3D volume and made of “rain-coat” material and suiting fabric “milana” to create a collection of modern youth clothing. The artistic and decorative design of the clothing collection with 3D volumetric ornaments was formed, and modern clothing models that meet the tastes of youth, fashion trends, and market requirements were developed.

A Study on the Improvement of Power Density of Axial Flux Motors for Collaborative Robot Joints through Same-Direction Skew

Axial flux motors have a large output density with a large outer diameter of the motor and a short axial length. Since it is advantageous in short axial length, the axial thickness of motor components becomes a very important parameter when designing axial flux motors. Among the components, the back yoke exists to serve as a path for magnetic flux and must have a certain thickness to prevent magnetic saturation. However, as the thickness of the back yoke increases within the axial size limit of the motor, the output of the motor may decrease. In this paper, same-direction skew that increases the cross-sectional area of the magnetic flux path without increasing the thickness of the back yoke is presented. Same-direction skew is a way to increase the cross-sectional area of the back yoke by skewing the rotor and stator in the same direction. The back yoke thickness that can be reduced by same-direction skew was calculated. Performance with same-direction skew designed using the equations was analyzed and compared, and the effectiveness of each type of rotor was verified. The validity of the proposed model was examined using the finite element analysis method.

Comparative investigation and optimization of a direct cooling structure for the primary core and windings in permanent magnet synchronous linear motors

The permanent magnet synchronous linear motors with high acceleration and high thrust density are favored in many applications, but accompanied by a rapid temperature rise. This paper investigates a novel direct cooling structure for the primary core and windings, integrated with the advantage of a filler with high thermal conductivity. It can greatly reduce the thermal resistances between the heat source and the coolant and thus improves the cooling performance. Detailed numerical calculations and analysis are carried out to reveal the electromagnetic performance and thermal benefits of the direct cooling structure compared with the traditional back yoke cooling structure. In addition, an improved thermal network model is proposed with the help of numerical model. It can not only improve the calculation accuracy of the average winding temperature, but also predict the maximum temperature without additional computational burden. Furthermore, the improved thermal network model can be an initial design model to quickly optimize the direct cooling structure. Finally, experiments are conducted on a prototype to verify the excellent cooling performance of the proposed cooling structure and the effectiveness of the improved thermal network model.

A Study on Weight Reduction and High Performance in Separated Magnetic Bearings

Recently, high-speed motors are receiving a lot of attention in the industrial field. When driving a motor at high speed, the advantages include high power density, high efficiency, and miniaturization. However, the disadvantages of the high-speed operation of motors are mechanical and structural safety. This is because the bearings used in high-speed motors require characteristics such as precision and low friction. There are two prominent types of bearings mainly used in high-speed motors: rolling bearings and magnetic bearings. A feature of rolling bearings is that they reduce frictional resistance by contacting points or lines between the shaft and the bearing. However, the disadvantages of rolling bearings are high mechanical friction losses due to the need for contact with the lubrication system. Maintenance costs are high. For this reason, a lot of research on bearings is being conducted to reduce the frictional loss of bearings and increase their efficiency and reliability. Bearings that are advantageous for high-speed operation are magnetic bearings that do not require lubricants, have no friction loss, and have low maintenance. However, magnetic bearings have disadvantages such as high cost and difficulty in miniaturization. In this paper, a stator with a separated teeth structure was used to compensate for these disadvantages. Using this, a model with miniaturization, light weight, and high manufacturability was proposed. The model name proposed in this study is called the STMB (separated teeth magnetic bearing). There are also disadvantages of the STMB model proposed in this paper. A model that compensates for this drawback is called the HSTMB (hybrid separated teeth magnetic bearing). The HSTMB reduces the weight by removing the back yoke of the stator and has advantages of a high filling rate and high productivity in the form of a module. As a result, high productivity, light weight, and high performance are possible when the HSTMB is applied, which was proven through FEA (finite element analysis).

Temperature Calculation, Test and Structure Improvement of Magnetic Coupling under High Slip

The temperature effect caused by high slip has an important influence on the operation performance and reliability of magnetic coupling. Taking the self-developed single disk asynchronous magnetic coupling as the research object, the heat loss equation of the magnetic coupling is established. Based on the three-dimensional transient magnetic field simulation model of the magnetic coupling, the eddy current loss, torque, and eddy current distribution law of the magnetic coupling are obtained through simulation. The space flow field and structure temperature field distribution of the magnetic coupling are analyzed by using the fluid-thermal coupling simulation method, and the heat dissipation coefficient and temperature distribution law of the structure surfaces such as copper disk, the back lining yoke iron disk, and the aluminum disk are obtained. The test platform was built to test the torque and temperature of the magnetic coupling. The results show that the error between the test and simulation is 4.8% in the torque aspect, and the maximum error between the test and simulation is only 8.1% in the temperature aspect of each component, which further verifies the effectiveness of the simulation method. On this basis, three heat dissipation improvement schemes are proposed, including installing heat dissipation blocks, setting semicircular grooves on the back lining yoke iron disk, and a hybrid design. The results show that the degree of improvement for each scheme is in the following order: hybrid design, setting semicircular grooves on the back lining yoke iron disk, and installing heat dissipation blocks. Under the hybrid design, the temperature of the back lining yoke iron plate and a copper plate of the magnetic coupling is reduced by about 8.5 °C compared with the original model, and the effect is ideal. The research results can provide an optimization reference for high-speed magnetic coupling and the temperature effect caused by an overload-locked rotor.

Design for Reducing Bearing Force Ripple and Torque Ripple of Integrated Magnetic Bearing Motor through Halbach Array

When a magnetic bearing is used in the design of a high-speed motor, no friction and wear occur because of the principle of magnetic levitation; however, the size of the entire system increases. An integrated magnetic bearing motor is a motor with a magnetic bearing inserted inside the rotor that can minimize the increase in the size of the entire system. In this study, a method to reduce the bearing force ripple and torque ripple of an integrated magnetic bearing motor through parameters for a Halbach array and permanent magnet tapering is proposed. When designing an integrated magnetic bearing motor, because the magnetic bearing is located inside the rotor, the influence of the magnetic flux of the rotor and stator on the magnetic flux of the magnetic bearing should be minimized. By combining the magnetic fluxes of the magnetic bearing, rotor, and stator at the rotor back yoke, magnetic saturation occurs, and the performance of the bearing force and torque ripples decreases. The bearing force and torque according to the Halbach array and permanent magnet tapering were analyzed using finite element analysis. The average bearing force and torque were maximized, and the ripple was minimized through the rotor parameters. Thus, the validity of the main design variables selected to improve the output characteristics was confirmed.

Back Yoke Design of Axial Flux Permanent Magnet Motors with Fractional-Slot Concentrated Winding for High Power Density

Back Yoke Design of Axial Flux Permanent Magnet Motors with Fractional-Slot Concentrated Winding for High Power Density

Numerical simulation of a high-power density 10 MW REBCO superconducting synchronous generator cooled by sub-cooled LN2 for low AC loss

Generators used in electric aircraft require a high-power density, and AC loss is also a significant problem. We designed 10 MW REBCO superconducting synchronous generators at 64 K to achieve a power density of 20 kW/kg and low AC loss. In this study, electromagnetic analyses were performed using finite element method software. Consequently, the thickness of the back yoke is 50 mm or less so that the generator can meet the target power density. The method of decreasing the magnetic field of the armature winding and increasing that of the field winding was used to effectively reduce the AC loss. As a result, the generator achieved a high-power density of 21.0 kW/kg, reducing the AC loss from over 600 kW to 415 kW.

A Study on the Improvement of Torque Density of an Axial Slot-Less Flux Permanent Magnet Synchronous Motor for Collaborative Robot

In this paper, an axial slot-less permanent magnet synchronous motor (ASFPMSM) was designed to increase the power density. The iron core of the stator was replaced with block coils, and the stator back yoke was removed because 3D printing can provide a wide range of structures of the stator. The proposed model also significantly impacts efficiency because it can reduce iron loss. To meet size and performance requirements, coil thickness and number of winding layers in the block, the total amount of magnet, and pole/slot combinations were considered. The validity of the proposed model was proved via finite elements analysis (FEA).

A novel squirrel cage eddy current coupling with adjustable radial air gap and its performance analysis

A novel squirrel cage eddy current coupling with adjustable radial air gap was presented, which can change the output speed by changing the air gap thickness in radial direction between the copper strips and the permanent magnet. It has the advantages of no axial force in speed regulation and less eccentric force in axisymmetric structure. The 2-D electromagnetic torque model of the rotor was established, and the influence of the air gap thickness on the electromagnetic torque was also studied by finite element method. Further, a novel method to solve the dynamic equation of the eddy current coupling was proposed based on the effect of air gap thickness and relative speed on torque characteristics, and was applied to the speed regulation performance analysis. In addition, the influence of the relative magnetic permeability of the permanent magnet back yoke and the internal rotor on the speed regulation performance was studied.

A micro electromagnetic actuator with high force density

In this paper, we propose a planar type micro electromagnetic actuator with high force density. The actuator is composed of a mover (8 mm*8 mm*0.5 mm) and a stator (14mm*10mm*0.2 mm). As the mover, a thick NdFeB permanent magnet film (300 μm) with a chessboard pattern (unit size is 0.8 mm*0.8 mm) is attached with a ferromagnetic back yoke to provide enhanced magnetic flux density. In the stator, 3D mesh type micro coil with multi-turn configuration is designed accordingly. The micro coil has a novel connection between adjacent mesh units, which enables easy fabrication. The thick film magnet with chessboard pattern as well as the multi-turn micro coil with novel connection constitute the originality of this actuator. The mover and the stator can be produced by batch fabrication. The magnetic flux density (B) generated by the magnet are simulated and experimentally measured. The magnitude of B at vertical direction attains around 40 m T at 770 μm plane above the surface. Due to delicate design, the MEMS-based micro coil can withstand as high as 0.4A constant current input for over 60 min on a thermal isolated ceramic plate. The long-time duration experiment testifies the practicality of this micro actuator. Both repulsive and attractive electromagnetic force can be generated on the mover by altering the current direction in the stator. The measured force is around 4.3 mN at 20 μm gap with 0.1A stable current input in the stator and the force density attains as high as 0.96 mN/A/mm3.

Performance Improvement of Spoke-shaped Interior Permanent Magnet Magnetic Gear

Magnetic gears have several advantages such as having low acoustic noise and being maintenance-free because there is no mechanical contact. Among these gears, the flux-modulated type has a higher torque density and efficiency than the other types. Therefore, it is expected to be put into practical use. In previous papers, a spoke-shaped interior permanent magnet (IPM) rotor structure was proposed in order to reduce the eddy current loss in magnets. This paper presents three methods for improving the performance of the spoke-shaped IPM magnetic gear. First, the position of the magnetic bridges is changed from the air gap side to the back yoke side to increase the effective magnetic flux. Second, amorphous alloy is used for the rotor core and pole pieces in order to reduce iron loss. Third, bonded Nd-Fe-B magnets for canceling the leakage flux are arranged to sandwich the inner rotor from both sides. As a result of prototype tests, the measured maximum torque of the proposed spoke-shaped IPM magnetic gear was 44% higher than that of the conventional one. In addition, the measured maximum efficiency reached 99.85% at 100 rpm.

Design study of an aerospace motor for more electric aircraft

This study proposes an improved power density permanent magnet synchronous motor (PMSM) for more electric aircraft (MEA) and conducts a design study on aerospace motors. To improve the power density of PMSM, a dual permanent magnet structure using high-temperature resistant high-performance permanent magnets and high-performance soft magnetic alloy material is creatively designed. Methods of lightweight structure designed in both stator and rotor meanwhile are combined as another mean to increase power density. The optimisation models for 6-slot/8-pole and 12-slot/10-pole configurations are first established based on finite element analysis. Methods of improving the power density of PMSM are then given, including minimum core back yoke thickness and lightweight structure design. The electromagnetic characteristics of the optimised machine are analysed by finite element analysis software, including back electromotive force (back-EMF), inductance, and power loss. The configuration of 12-slot/10-pole is selected as the best design scheme for MEA, based on which a prototype is manufactured and tested. The experiment results of cogging torque and line back-EMF are in good agreement with the simulation results, which shows the rationality of the designed new machine. The design proves to be effective for improving the power density of aerospace motors.

Analysis of Superconducting Synchronous Motors With Halbach Array Field Excitation

This article evaluates the novel design approach of a 3 MW partially superconducting synchronous machine for electric aircraft propulsion. Its special feature is the application of an electromagnetic Halbach array for the field excitation to reduce the back yoke weight and thereby increase the overall output power density. The electromagnetic Halbach array is obtained by reproducing a permanent magnet Halbach array with high-temperature superconducting coils. The arrangement is further optimized, and its field characteristics are compared to a conventional superconducting field winding design. Even though the Halbach array has a higher space and superconductor consumption, it shows better characteristics concerning the intensity of inside and outside magnetic field. Applied in a superconducting motor, the Halbach array field winding achieves a back yoke thickness reduction of up to 85% and a back yoke weight reduction of up to 78% compared to reference models. The gravimetric power density is increased by up to 30% at the expense of volumetric power density. In exchange for a back yoke weight reduction, other components, such as field winding and cryostat, become heavier.

Investigation of Structure and Material for Back Yoke at 13.56 MHz Wireless Power Transfer Focused on High Transmission Efficiency

Wireless power transfer (WPT) is a technique to send electricity without the need for a mechanical point of contact. Because of the widespread use of WPT technology, fast charging speeds and space saving devices are desired. Therefore, in order to shorten the charging time, suitable materials and structures of the back yoke were examined. We made a core and cap-shaped back yoke using an amorphous powder with low loss. As a result, the transmission efficiency in the ideal state increased by 0.7%, and at 50 W transmission, it increased by 1.2%.

Tolerance Sensitivity Analysis and Robust Optimal Design Method of a Surface-Mounted Permanent Magnet Motor by Using a Hybrid Response Surface Method Considering Manufacturing Tolerances

This paper presents a robust optimal design method using a hybrid response surface method (H-RSM) which directly finds an optimal point satisfying a target Z-value or a probability of failure. Through three steps, this paper achieves the goal that is to increase the open-circuit airgap flux (OCAF) in a surface-mounted permanent magnet motor and decrease its variation caused by variations of the airgap lengths including an additional one between permanent magnets and rotor back yoke. First, the OCAF equation is derived from the magnetic equivalent circuit (MEC) considering the additional airgap. Then, the equation is validated by comparing its results with those of the finite element method (FEM) modeled by the slotless stator. Next, the tolerance sensitivity analysis, using the partial derivative of the OCAF equation with respect to the airgap length, is performed to investigate the effects of design variables on the OCAF. It is shown that increasing the magnet thickness is effective for both increasing mean of the OCAF and reducing its variation. Finally, robust optimal design is performed using the H-RSM, in which all data are obtained from the FEM modeled by the slotted stator. The results of the robust optimal design are verified using the FEM.

Design, experiments and multidisciplinary optimization of 2 degrees-of-freedom electromagnetic actuator for application in space vibration isolation

Considering space environmental requirements, a multidisciplinary optimization of a 2 degrees-of-freedom micro linear actuator is carried out to improve the overall performance of a nested flying vehicle in this article. To achieve high-quality microgravity environment, a nested flying vehicle is designed that can be operated inside the Space Station. The electromagnetic actuators are utilized to control the position and posture of the experiment device while the exterior structure is following the movement of the inner system. Each actuator is designed to generate vertical and horizontal forces at the same time. The actuator is composed of two permanent magnets, a 2 degrees-of-freedom coil on a printed circuit board and a steel back yoke. Due to the complexity of structure parameters modification, the geometry, the structural model, electromagnetism model, and multidisciplinary analysis process are integrated based on ModelCenter framework. In this case, the structural model is established using ANSYS/APDL. The electromagnetic analysis is performed by the magnetics postprocessing. The OPTLIB Gradient Optimizer, non-dominated sorting genetic algorithm II, and Design Explorer for multidisciplinary optimization with constraints are utilized for validation mutually. In view of the optimization results, compared with the prototype design based on experience, the width of the back yoke, the weight of actuator, and the residual force have been reduced by 23%, 50%, and 62% while the output forces resulted in an acceptable range.

Analysis of the primary experimental results on a 5 cm diameter ECR ion thruster

An ECR ion thruster with a diameter of 5 cm has been developed and tested. Four different antenna positions were experimentally and numerically investigated, and the results suggest that the optimal location for the antenna is where it is perfectly surrounded by the electron cyclotron resonance layer. We also evaluated two different antenna configurations, and found that the star configuration is preferable to the circular configuration, and also that the circular antenna is only 40% as efficient as the star antenna. The experimental curve of the ion beam current and voltage agrees with the fitting results from the analytic solution. The simulation of the magnetic topology in the discharging chamber with different back yoke heights indicates that it needs to be further verified.

Thin resolver using the easy magnetization axis of the grain-oriented silicon steel as an angle indicator

A new type of thin resolver is presented, in which the easy axis of the magnetic anisotropy in the grain-oriented silicon steel is used as an angle indicator. The total thickness including a rotor, PCB coils and a back yoke can be made less than 4 mm. With a rotor of 50 mm diameter, a good linear response (non-linearity error < 0.4%) between the mechanical angle input and the electrical angle output has been obtained. The influence of a weak magnetic anisotropy in the non-grain-oriented silicon steel used for the back yoke on the accuracy of the resolver can be deleted by the method proposed in this paper.

대형 전동기에서의 영구자석 철 받침대와 요크 간의 전자기 결합력 향상에 관한 연구

대형 전동기에서의 영구자석 철 받침대와 요크 간의 전자기 결합력 향상에 관한 연구