Analysis of moving magnet linear dc motor with two straight stators

The thrust force of moving magnet-type linear direct current motors (MM-LDM) is analyzed in this study. A moving magnet-type MM-LDM consists of a stator and a carriage. The stator is composed of two stick shaped electromagnetics and the carriage consists of a movable permanent magnet that is located between the two electromagnets. One of the methods for calculating the thrust force of an MM-LDM is to analyze the energy gradient which is determined by the distribution of magnetic flux. However, this method is very difficult when used to calculate the thrust force of this kind of LDM. This type of MM-LDM can be considered to be a transformer in which the magnet of the mover is assumed to be a one-turn coil carrying a large current. The stored energy in the MM-LDM can be obtained by measuring the self-inductance and the mutual-inductance of the equivalent circuit of the MM-LDM. And this energy gradient gives the thrust force. The calculation of the thrust force induced in this motor shows that the mutual inductance has a large influence on the generation of thrust force.     

Design investigation of a linear motor for artificial heart driving

The authors have been considering the use of a linear pulse motor (LPM) as a driving source of a totally implantable artificial heart (TAH), and have developed a series of artificial heart models that incorporate such a motor. The newly developed linear-type TAH (linear TAH) has two blood-pumps, which are inflated and deflated alternately by the LPM, causing a pusher plate to pulsate the blood. This paper deals with the performance calculation of the LPM using the loading ratio. Some motors manufactured for driving TAHs were then selected to compare their machine parameters. The selected motors were LPM, linear oscillatory actuator, brushless dc motors, and ultrasonic motor. Two parameters were selected for the comparison: the mechanical output/volume ratio and the motor constant. The results may be summarized as follows: 1. The LPM was designed based on the loading ratio, and the kinetic thrust and velocity were obtained at the range of 77 newtons and 80 mm/s, respectively. 2. The loading ratio of the LPMs were more than eight times larger in comparison with the rotary motors that were used in industrial machines. 3. The motor constants of the LPMs were recognized to be one figure larger than that of the brushless dc motors. In order to reduce the volume of the linear TAH, it is necessary to increase the drive velocity of the LPMs. Application of the linear motor to a nonpulsatile artificial heart will be one way to achieve this. © 1998 Scripta Technica, Electr Eng Jpn, 123(1): 43–50, 1998     

Relation between thrust constant and size in design of moving-coil linear dc motors

In this paper, the relationship between the limit value of the thrust constant and size of a linear dc motor (LDM) of moving coil type with unipolar design is described. The relationship between the limit value of the thrust constant of the LDM and the dimension of the yokes is deduced. Its relation is defined as the relational equation. To maximize the ratio of thrust to the volume of LDM, the magnetic flux density in the yoke is adjusted to the value of magnetic saturation. As a result, the following can be observed: the thrust constant is in inverse proportion to the stroke and is proportional to the sectional area of the center yoke. By measuring the thrust of the LDM and using the results of magnetic field analysis (finite element method), the validity of this observation is confirmed. The relation qualitatively agrees with the measurements, and its maximum error is 26.0 percent. Two LDMs are designed to verify the accuracy of our relational equation. One LDM is thin (maximum thickness is 14 millimeters) with long stroke (100 millimeters) for a pen recorder. The other LDM is for a high-speed positioning system with strong thrust (20 newtons). The relational equation agrees well with the measured thrust constant, with an error of about 14 percent. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 45–54, 1998     

Two‐dimensional dc surface motor using window‐shaped coils

The authors have been pursuing the possibility of using a two‐dimensional dc motor as a driver for a dining assistance apparatus. In this paper, a new type of dc surface motor using window‐shaped coils (DSM) is proposed by the authors. Equations describing the relation between the excitation mode of the window‐shaped coils and the thrust are derived. The driving characteristics of the DSM are summarized as follows: 1. The maximum flux density of the air gap is calculated to be 0.35 T when the exciting current is 1.8 A. The flux density actually obtained is only 20% of the maximum flux density magnitude (1.8 T) of the yokes (SS41). 2. The thrust constants in the x and y directions are 2.93 and 2.70 N/A, respectively, showing a discrepancy of only 8%. The maximum static thrust is over 5 N when the exciting current is 1.8 A. 3. Good positioning accuracy of 7.5% was achieved when the DSM was subjected to the PD control method. © 1999 Scripta Technica, Electr Eng Jpn, 128(1): 70–77, 1999     

Finding all solutions of piecewise‐linear resistive circuits using the dual simplex method

An efficient algorithm is proposed for finding all solutions of piecewise‐linear (PWL) resistive circuits using linear programming (LP). This algorithm is based on a simple test (termed the LP test) for non‐existence of a solution to a system of PWL equations in a given region. In the conventional LP test, the system of PWL equations is transformed into an LP problem, to which the simplex method is applied. However, this algorithm requires a very large number of pivotings because the simplex method is applied on many regions. In this paper, we introduce the dual simplex method to the LP test, which makes the average number of pivotings per region much smaller (less than one, for example) and makes the algorithm very efficient. By numerical examples, it is shown that the proposed algorithm could find all solutions of large‐scale problems, including those where the number of variables is 300 and the number of linear regions is 10³⁰⁰, in practical computation time. Copyright © 2002 John Wiley & Sons, Ltd.     

Considerations on the thrust‐to‐input ratio of a cylindrical moving‐coil‐type linear dc motor

Linear dc motors (LDMs) are widely used for servo‐actuators, compressors, and so on. High‐efficiency LDMs are strongly desired for compressors. To realize LDMs with high‐efficiency characteristics, decreasing the copper losses, namely, thrust‐to‐input ratio, F/P, must be increased. This paper describes an optimization method for the F/P of a moving‐coil‐type LDM. The following results are obtained:

• 1 Simplified expression for the F/P of the LDM is derived from the permeance analysis method. The effects of dimensions of the LDM on the F/P of the LDM are investigated through the simplified expression for the F/P. As a result, the optimum dimension of the LDM for maximizing the F/P exists.
• 2 When the static thrust is 100 N, the measured F/P of the initial LDM is 7.9 N/W, and the errors using the simplified expression for the F/P and the finite element method (FEM) are 33 and 8%, respectively. Derived simplified expression for the F/P is useful because the F/P can be calculated easily.
• 3 An improved LDM, which has 26% higher F/P than those of the initial LDM, is designed by using the permeance analysis method and the FEM. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 103–111, 2000

     

分段直线感应电动机起动性能的计算和分析

为了提高长初级直线感应电机的效率,节约电能,在实际应用中需要将其初级分段。以分段长初级直线感应电机为研究对象,采用有限元方法,建立了电机的电磁场计算模型,同时运用虚功法来计算电机的电磁力。通过ANSOFT仿真,研究了电机的空载启动、运行及堵转过程,得出了电机的推力、位移、速度曲线及电机内部电磁场的分布特点。最后,利用 Maxwell2 D软件的有限元法分析了长初级直线感应电机起动推力随气隙大小、分段间距以及启动位置的变化规律。所得到的计算方法与规律对分段长初级直线感应电机的优化设计和制造能提供有益帮助。     

Optimum design of a long-stroke thin linear DC motor

Computers have been more widely used in recent years. Researchers are now able to analyze a magnetic field using the finite element method. A motor can be designed more effectively and rationally. It is important to understand design space. Design space means the limit of the thrust or design variables within constraints. Within these limited dimensions, a linear dc motor (LDM) for a pen recorder is designed. This LDM is very thin with long strokes. It is described as follows: (1) the thickness of the permanent magnet and the length of the gap are selected as the design variables in the magnetic circuit of the LDM; (2) the effective magnetic flux density of LDMs using the 3-D finite element method is compared; (3) the design space of thin LDM with long strokes is clarified. The LDM measurement value (thrust constant) was increased at 0.60 N/A from the first LDM. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (4): 84–93, 1997     

Mover design and performance analysis of linear synchronous reluctance motor with multiflux barrier

A synchronous reluctance motor has many advantages because it has no permanent magnet, such as low back emf in high‐speed operation, maintaining performance in a high‐temperature environment, and so on. Therefore, many rotor constructions have been studied and developed. The rotor with multiflux barrier structure has the merit of easy construction and high performance. The linear synchronous reluctance motor has been developed. It is necessary to improve the performance of the mover design for industrial use, because of its low power factor. In this paper, we propose a novel configuration of mover for the linear synchronous reluctance motor, and examine the static characteristics of the motor with reluctance equalization design by means of the finite element method. From analytical results, it is demonstrated that the static characteristics of the linear synchronous reluctance motor are greatly improved by the reluctance equalization design at the iron layer in the mover. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 61–69, 2002; DOI 10.1002/eej.1139     

Levitation and propulsion for a magnetically levitated conveyance system using a two‐phase linear motor

Magnetically levitated conveyance systems have been developed. Most consist of a levitation (and guidance) section and a thrust section. We have developed a conveyance system that realizes levitation and propulsion with a single facility using a two‐phase linear motor. In this system, the levitation and propulsion system are combined. The control method for the propulsion system to achieve more stability is discussed. To obtain the propulsion force, modulation of the voltage applied on the primary windings is undertaken. A traveling field is generated and applied to a carrier with a secondary iron core. The levitation force is produced by attraction between the flux generated by the primary windings and the secondary iron core. Because we need only electrical power for FET switching on the carrier side, no power supply system for the carrier is needed. Experimental results indicate that this system realizes contact‐less conveyance with various propulsion patterns. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(3): 65–72, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20551     

An interval algorithm for finding all solutions of non‐linear resistive circuits

In this letter, an efficient algorithm is proposed for finding all solutions of non‐linear (not piecewise‐linear) resistive circuits. This algorithm is based on interval analysis, the dual simplex method, and the contraction methods. By numerical examples, it is shown that the proposed algorithm could find all solutions of systems of 500–700 non‐linear circuit equations in acceptable computation time. Copyright © 2004 John Wiley & Sons, Ltd.     

3D numerical analysis and test results of a short‐primary linear reluctance motor

A 3D boundary integral equation is applied to a model of a short‐primary linear reluctance motor. The model is a double‐sided construction where the primary member is surrounded by a set of secondary iron plates on both sides. Six kinds of different secondary geometries are calculated and their characteristics are discussed. For the confirmation of calculation results, a test machine is manufactured. Test results are compared with calculated ones. Furthermore, the static thrusts of a single‐sided machine and a coreless PMLSM are measured and compared with those of the double‐sided machine. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 58–65, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20390     

Study of drive system for linear induction motor using magnetic energy recovery switch

This paper proposes a power supply suitable for driving linear induction motors. The power supply consists of a voltage source inverter (VSI) and a magnetic energy recovery switch (MERS). Circuit configuration and operation principles of the power supply are described. Power factor correction by MERS can increase the output power. Technical advantages of using MERS compared with increasing the rated voltage of VSI are discussed. Some experiments with a linear induction motor were conducted. The results confirm that MERS can reduce the capacity of the VSI or increase the output with the same VSI capacity. The number of devices and magnitude of losses are evaluated on a large‐scale drive system. A half‐bridge type of MERS is provided and discussed. The half‐bridge MERS mitigates disadvantages of using MERS. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(4): 65–74, 2009; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20832     

Development of railgun accelerator at the institute of space and astronautical science (ISAS)

This paper describes the current status of the development of electromagnetic launchers such as the railgun at ISAS. The railgun is the most improved accelerator of Electromagnetic Launchers (EML). EML offers a potential for accelerating a projectile to much greater velocities than achieved with conventional powder guns or light gas guns. However, there has been little progress in increasing the velocity of EMLs since the experiment by Rashleigh and Marshall. A few experiments have been reported achieving velocities greater than 6km/s. The authors have achieved velocities greater than 6 km/s by reducing plasma leakage which is one of the factors limiting velocity. In this paper a 6 km/s launch is reported, compared with the results of two other shots considered from the viewpoint of plasma leakage, and the effect of entrainment of eroded material into the armature by rail ablation was discussed on the basis of simulated numerical calculations.     

低压差(LDO)线性稳压器结构的改进

为了提高LDO的负载瞬态响应,本文提出了一种新型的LDO电路结构,该结构提高了系统的带宽和转换速率,从而使LDO的负载瞬态响应和负载调整能力也得以提升。     

Rail brake system using a linear induction motor for dynamic braking

One type of braking system for railway vehicles is the eddy current brake. Because this type of brake has the problem of rail heating, it has not been used for practical applications in Japan. Therefore, we proposed the use of a linear induction motor (LIM) for dynamic braking in eddy current brake systems. The LIM reduces rail heating and uses an inverter for self excitation. We estimated the performance of an LIM from experimental results of a fundamental test machine and confirmed that the LIM generates an approximately constant braking force under constant current excitation. At relatively low frequencies, this braking force remains unaffected by frequency changes. The reduction ratio of rail heating is also approximately proportional to the frequency. We also confirmed that dynamic braking resulting in no electrical output can be used for drive control of the LIM. These characteristics are convenient for the realization of the LIM rail brake system. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(2): 29–38, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21209     

基于小波变换的磁悬浮直线电机故障诊断研究

在井下开发应用中,随着大量的井下电机泵应用,类似于石油等领域的应用.然而这些井下安装的机械设备工作环境恶劣,因此极易出现故障,甚至威胁生产安全.因此需要井下机械设备必须采用早期故障诊断来进行故障的预测,以达到减小损失的目的.井下油气开采领域大量采用的磁悬浮井下采油泵提高了采油的效率,对这种新型采油设备的间接故障检测手段几乎没有,通过间接的测试方法对井下磁悬浮直线电机进行故障检测.提出声学振动以及改进小波分析的方法对井下磁悬浮直线电机泵进行故障检测,通过分析,井下声传播信道的传播特点,得到声学信道特征,从而分析故障信号的传播通路,然后通过改进小波故障分析算法对故障进行分析识别,最终得出磁悬浮直线电机泵检测方法,通过试验,证实该方法具有较好的应用前景.     

A compensation method for the end effect of a linear induction motor

For the end effect of a linear induction motor (LIM), the authors propose a new concept that the end effect can be compensated for only by the supply of secondary current synchronized with the current of the LIM in front of the entry end of the LIM, without considering the flux density distribution in the LIM primary region. As a concrete method to supply the secondary current in front of the LIM, the authors propose the rotator with rare‐earth‐type permanent magnets which has a strong flux density without ohmic loss, and does not cause the power factor problem even for the influence of end effect. The results of analytical study on the numerical example of LIM designed for subways are as follows. This method can make the flux density and thrust density distribution in the LIM primary region almost entirely agree with those of the case without end effects. This method can compensate for the thrust, power factor, and efficiency of the LIM at the rated speed to coincide with the characteristics without end effect. There is no problem in the slip characteristic curves of the LIM with the compensator, although the compensator only rotates synchronizing with the frequency of the LIM. The effect of compensation becomes large in the lower slip. The force to rotate the compensator is very small in the suitable design. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 58–67, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10132     

On the design of high‐efficiency linear induction motors for linear metro

Linear metro with single‐sided linear induction motor (SLIM) propulsion and wheel‐on‐rail support and guidance came into service in April 1990 in Osaka and in December 1991 in Tokyo, and is under construction or planned for Yokohama, Kobe, and Fukuoka. Since the new traffic system is used widely, it is of great importance to decrease its energy consumption. In this paper, the design of the SLIM for the linear metro is formulated as a constrained nonlinear programming problem, and optimum design is carried out to maximize efficiency. Seven parameters are chosen as independent variables: number of poles, pole pitch, stack height, secondary aluminum sheet thickness, overhang length, slot width/slot pitch ratio, and rated slip. The output KW/input KVA ratio, maximum flux density in teeth, temperature rise, primary length, stack height, overhang length, maximum thrust, and vertical force are selected as constraint functions. In the optimization procedure, the performance characteristics are formulated by space harmonic analysis taking account of the end effect, skin effect, and air gap leakage. The accuracy of the formulas is verified against experimental results. Effective ways of increasing efficiency include the addition of a copper reaction plate and minimization of the mechanical clearance. © 2001 Scripta Technica, Electr Eng Jpn, 137(2): 36–43, 2001     

电磁调速电动机双速控制电路的改进

分析了电机控制回路的控制原理 ,指出了原控制电路中存在的不安全、不节能等实际问题 ,并给出了具体的改进措施