Permanent Magnet Volume Research Articles

Design and Analysis of a Novel 2-D Permanent Magnet Array for Planar Actuator

A novel 2-D permanent magnet array for a planar actuator was proposed, in which the portion between adjacent magnetic poles was divided to four small rectangular solids. Magnetic fields of the permanent magnet array were analyzed systematically by 3D finite element method. The analysis results show that, compared with the well-known Halbach magnet array, the proposed array has higher permanent magnet utilization. Keeping the whole permanent magnet volume constant, the arrays with several improved structures were put forward. The magnetic field analyze results prove that the utilization is best, when the ratio between the height of the magnetic poles magnetized vertically and the height of the portion magnetized horizontally is about 2.

Losses, Efficiency and Thermal Behavior of the Synchronous Motors with Different PM Materials

The paper deals with losses, efficiency and thermal behavior of the synchronous machines with different permanent magnet (PM) materials. Three PMSM are presented in this paper: First, the PMSM with NdFeB PM, which is really constructed. Second, the NdFeB was replaced by ferrites PM. Third, the new design of synchronous motor with ferrites is presented. The volume of PM and the whole size are increased to keep the same power output. Equivalent circuit parameters, EMF, V-curves, losses, efficiency and thermal behavior of all three machines are investigated and compared.

Design and Optimization of the New H-Module Linear Actuator

The single-sided linear actuator has usually large normal force which may induce large frictional force when using roll-bearings to support the linear motion. Otherwise, an air suspension system or assisted guide is needed to balance the normal force. A new H-module linear actuator (HMLA) with much lower normal force is proposed in this paper. The proposed new H-module linear actuator makes use of additional air suspension system unnecessary. The topology and working principle of the HMLA is illustrated in details in this paper. The force characteristics are analyzed by finite element method (FEM). The impacts of several key design parameters on the force characteristics are studied, and the HMLA is optimized afterwards. It is proved that the optimized HMLA could use less permanent magnet (PM) volume and generate larger useful tangential force and its normal force vs. tangential force ratio is much lower than that of the conventional single-sided linear actuator.

Permanent-Magnet Optimization in Permanent-Magnet-Assisted Synchronous Reluctance Motor for a Wide Constant-Power Speed Range

A permanent-magnet (PM)-assisted synchronous reluctance (PMASR) machine exhibits both high efficiency and high flux-weakening (FW) range. However, the best performance is achieved after a machine design optimization. In industry applications, the design of PMASR machines requires to satisfy an increasing number of limitations. The key points are lamination geometry, material property, and control strategy. This paper analyzes the influence of PM volume (flux level) on the motor performance, although lamination geometry and stack length are kept fixed. Thus, the PM volume inset in the rotor is optimized. The considered PMASR motor is designed for a very high FW speed range. The study is based on a finite-element (FE) analysis. The accuracy of the FE simulations is verified comparing their results with measurements on a prototype. The FE model is then used to study the different cases.

Demagnetization Analysis of Permanent Magnets According to Rotor Types of Interior Permanent Magnet Synchronous Motor

This paper shows a study on the demagnetization performance analysis of permanent magnet according to three kinds of rotor types of an interior permanent magnet synchronous motor (IPMSM). It is very important to consider demagnetization performance as well as motor performance such as rated torque, output current, and efficiency when designing IPMSM. Three kinds of rotor types according to permanent magnet arrangement; single layer type, v shape type, and double layer type are generally used for IPMSM. In the paper, the magnetic equivalent circuits according to each rotor type are proposed in order for initial design of thickness of permanent magnets considering demagnetization by lumped constant related to magnetic circuit. The volume of permanent magnets per pole and back EMF of each rotor type is assumed to equal for the comparison of demagnetization of IPMSMs with same performance each other. Next, distribution of demagnetization in the permanent magnet is analyzed by using finite element method (FEM) for the verification of the results by magnetic equivalent circuit.

Analytical Calculation of No-Load Voltage Waveforms in Machines Based on Permanent-Magnet Volume Integration

We develop an analytical expression for predicting electromotive force (EMF) waveforms resulting from permanent magnets (PMs) in electrical machines. The expressions for the flux linkage are based on a volume integral over the magnet volume, rather than the usual surface integral over the coil. The proposed method consists of applying a virtual current in the coil of the machine and calculating the magnetic field generated inside the PM volume. The EMF waveform is obtained by taking the derivative of the flux linkage with respect to time. We present analytical expressions of the EMF for various PM shapes and Halbach magnetization patterns. We tested a total of four configurations of PMs, and the experimental waveforms confirmed the validity of the expressions obtained theoretically.

이동통신 단말기용 통합 영구 자석 형태의 마이크로스피커 개발

In mobile phones of multimedia era, microspeakers of high qualify sound are essential parts to generate human voice in speaker phone and MP3 song player. In this paper, two types of microspeakers, outer permanent magnet (PM) and combined PM type, are analyzed using electromagnetic, mechanical and their coupling analysis. For performance comparison, voice coil diameter is chosen as a design parameter to change excitation position and magnet volume for both types. For combined PM type, sound pressure level (SPL) is improved due to increased PM volume compared to outer PM type. Also, with the decreased voice coil diameter for combined PM type, the 1st resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range. Therefore, it can be said that the combined PM type microspeakers are more advantageous for high performance microspeaker which are essential for multimedia era.

New development of combined permanent-magnet type microspeakers used for cellular phones

In mobile phones of multimedia era, microspeakers of high-quality sound are essential parts to generate human voice in speaker phone and MP3 song player. In this paper, two types of microspeakers, outer permanent magnet (PM) and combined PM type, are analyzed using electromagnetic, mechanical, acoustical and their coupling analysis. For performance comparison, voice coil diameter is chosen as a design parameter to change excitation position and magnet volume for both types. For combined PM type, sound pressure level (SPL) is improved due to increased PM volume compared to outer PM type. Also, with the decreased voice coil diameter for combined PM type, the 1st resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range. Therefore, it can be said that the combined PM type microspeakers are more advantageous for high performance microspeaker which are essential for multimedia era.

Pulsed field magnetometery for high coercivity permanent magnets

A high sensitivity pulsed field magnetometer for the measurement of thin films or small volume of high coercive rare earth permanent magnets has been constructed. The pickup coil designed in principle of 3-axis compensation has the sensitivity of 5×10−4 emu at tested field of 76 kOe. The compensation has been repeatable within 4×10−4–10×10−4 emu, which is enough for measurement within 2% accuracy for the materials with magnetic moment as small as 5×10−2 emu. Measurements on NdFeB magnet show excellent repeatability within 0.3% discrepancy for remanence and coercivity. The magnetic hysteresis loop of a NdFeB thin film (1050 nm) was measured satisfactorily. Estimation of the eddy current effect, by measuring the similar dimensioned but lower resistive nonmagnetic metals, has also been investigated.

Varying magnetization orientation for permanent-magnet volume reduction in machines

We present an enhanced version of a method to minimize the amount of permanent-magnet (PM) material required to create a certain flux linkage in the stator winding of a PM machine. The enhanced version obtains the distribution of the factor /spl delta/ inside the PM; /spl delta/ identifies the areas inside the PM volume where the orientation of magnetization may be modified, so as to further increase the amount of no-load flux linkage generated by the PM per cubic meter of PM material. The paper shows how this method can be used with increased benefits in machines with small pole pitches. The case of a transverse-flux permanent-magnet (TFPM) machine with a pole pitch of 1 cm is analyzed. The resulting PM design shows an improvement of 48% of the amount of flux linkage created per volume of PM material, for the same air-gap thickness and magnet thickness.

Contribution of permanent-magnet volume elements to no-load voltage in machines

In permanent-magnet (PM) electrical machines, a key role of PM material is to induce a voltage in a winding upon a relative movement of the PM about that winding. Although useful, PMs are costly and machine designers should optimize the contribution of all the volume elements in PMs as much as possible. This paper presents a new mathematical expression for the no-load flux linkage generated by PMs. The mathematical expression gives the flux linkage in terms of the PM geometry. This proves to be efficient in evaluating the contribution of each local magnet volume element to generate a no-load flux linkage. We propose a method that uses the derived mathematical expression to optimize the shape of PMs, and this method is applied to the case of a conventional PM synchronous machine. The optimization process uses the results from finite-element analysis, and the resulting PM shape shows an increase of voltage induced per PM volume.

Magnet shaping for minimal magnet volume in machines

An expression for the no-load flux linkage in permanent-magnet (PM) machines is derived. From this expression, a method, is proposed to increase the no-load flux linkage generated in a stator winding per volume of PM material. The method is suitable for machines with short pole pitch and is applied to a transverse-flux machine with single-sided surface-mounted PM. The result is an increase of 37% of the no-load flux linkage per volume of PM, compared with the case of rectangular PM covering 100% of the pole pitch. An increase of 15% is also obtained, if compared with the common practice of using PM covering 80% of the pole pitch.

Optimal design of efficient IPM motor using finite element method

Techniques for the optimal design of permanent magnet motors considering rotation are investigated. The nonconforming mesh technique is used to take into account the rotation of the rotor. It is shown that the technique is especially useful for the optimal design using the finite element method, because no modification of mesh is necessary during the rotation. The mesh at each angle of rotation can be obtained by only combining meshes of a rotor and a stator. By using the combined optimization technique of the experimental design method and Rosenbrock's method, the number of FEM calculations can be reduced. By applying the optimal design method, about 40% of volume of permanent magnet of IPM motor and about 15% of the torque ripple can be reduced.

Machine Parameters and Performances of Interior Permanent Magnet Synchronous Motors with Different Permanent Magnet Volume

Permanent magnet synchronous motor (PM motor) is widely used for several industrial applications. Some applications such as an electric vehicle and a compressor drive require a constant power operation. The operating limits and the constant power speed range deeply depend on the machine parameters. The relationships between the motor parameters and the operating performance have been theoretically examined. This paper examines the performances of the prototype synchronous motors, where a stator structure and a rotor structure of all motors are the same. The permanent magnets are inserted into the rotor slits and the volume of permanent magnet is adjusted to control the magnet-flux linkage. The effects of adding magnet into the rotor on the machine parameters and the operating performance are examined based on the various experimental results. The prototype motor has flexibility on the speed versus power performance by adjusting the volume of permanent magnet. The theoretical results with respect to the operating limits and the motor parameters are also confirmed experimentally.