Simulation and detection of dynamic air-gap eccentricity insalient-pole synchronous machines

This paper presents the effect of dynamic air-gap eccentricity on the performance of a salient-pole synchronous machine. The modified winding function approach (MWFA) accounting for all space harmonics has been used for the calculations of machine winding inductances. In addition, the winding inductances have been calculated by the finite-element method to support those calculated by the MWFA. Relationships between stator-current-induced harmonics and dynamic air-gap eccentricity were investigated. The coupled magnetic circuits approach has been used for modeling the synchronous machine performance under the dynamic air-gap eccentricity. Finally, experimental results to substantiate the theoretical findings are presented     

Determination of effective air-gap length of synchronous reluctance motors (SynchRel) from experimental data

The usage of synchronous reluctance motors (synchRel) has been gaining importance in many industry applications mainly because of their many advantages over other motors. The performance of a synchRel is greatly dependent on its effective air-gap lengths along the d and q axes. Hence, in this paper, an attempt has been made to obtain the effective air-gap lengths of the machine from the experimental values of the d and q axes reactances and by considering the higher permeance and winding space harmonics. To determine the air gaps, these reactances are compared with their corresponding expressions involving the coefficients of magnetizing and mutual inductances of the stator windings, obtained by using the winding function approach (WFA). Using these air-gap values, a more realistic model of the machine is obtained. A comparative study has been carried out with different permeance and winding space harmonics. The computed q-axis air-gap length seems to be much more sensitive to the operating point and the leakage inductance, compared to the computed d-axis air-gap length. Experimental values near the no-load condition have been considered to minimize flux barrier effects, as WFA cannot simulate these effects without changing the length of the pole arc. The effective air gaps of another salient-pole synchronous machine with damper bars have also been determined by considering the higher permeance and winding space harmonics, when run as a synchRel (without field excitation). This machine did not have flux barriers, and, hence, the results seem to be more accurate. Finally, the performance of the simulated synchRel has been compared with the experimental results.     

EXPERIENCE WITH DIRECT AND INDIRECT SEARCH METHODS APPLIED TO CAGE INDUCTION MOTOR DESIGN OPTIMIZATION

Abstract

In the present paper low cost cage induction motor design problem is approached using direct search methods, which do not require to calculate the derivatives of the function, and indirect method-a penalty function approach. Induction motor design is considered as a nonlinear, multivariable constrained optimisation problem with ampere conductors per meter, ratios stack length to pole pitch and stator slot depth to width, stator core depth, average air-gap flux density, and stator and rotor winding current densities as variables. The constraints are imposed on the thermal ratings of the machine and on performance indices- Results for same capacity motor with different optimization techniques are tabulated and compared.     

高频电感气隙布置与绕组损耗的分析

针对高频电感的绕组损耗问题,利用有限元数值分析,研究了气隙位置的变化对电感器绕组损耗的影响,比较了不均匀分布气隙与均匀分布气隙对绕组损耗的影响,并对分布气隙参数提出了合理的设计原则.结果表明：气隙位置开在拐角处会增加绕组损耗.相对于不均匀分布气隙,均匀分布气隙有利于减小绕组损耗,且可以将分布气隙个数增加到使绕组距气隙的避让距离控制在3～5个气隙距之间,同时分布气隙间磁柱的长度大于6个气隙距,以得到较小的绕组损耗.     

Bacterial Foraging Based Optimal Design of Transverse Flux Linear Motor for Thrust Force Improvement

Abstract—This article presents a novel optimal design for a permanent magnet excitation transverse flux linear motor with an inner mover using bacterial foraging optimization. The target is maximizing the motor thrust force, which is the most important quantity in linear electric drives. The stator pole length, air-gap length, winding window width, and stator pole width define the search space for the optimization problem. The response surface methodology is used to build the mathematical model of the motor thrust force in terms of the design variables. It can create an objective function easily, and great computational time is saved. Finite-element computations are used for numerical experiments on the geometrical design variables to determine the coefficients of a second-order analytical model for the response surface methodology. The bacterial foraging optimization technique is used as a searching tool under the constraints of design variables for design optimization of the transverse flux linear motor to improve the motor thrust force. The effectiveness of the proposed bacterial foraging optimization model is then compared with that of both genetic algorithm and particle swarm optimization models. With this proposed bacterial foraging optimization technique, the thrust force of the initially designed transverse flux linear motor can be increased.     

A Novel PMSM with Optimized Asymmetric Eccentric Air-Gap for High-Power Electric Motorcycle

Abstract

In order to improve power density of high-power electric motorcycle driving motor, the air-gap length is usually minimized, which aggravates the influence of armature reaction on air-gap magnetic field. Considering the fact of unidirectional driving of electric motorcycle, the eccentric air-gap is used in each pole air-gap magnetic field strengthened area to suppress armature reaction, thus an asymmetric eccentric air-gap structure is designed. The torque and efficiency of motor are improved by asymmetric structure optimizing to improve the comfort, load capacity and battery life of vehicle, the ratio of maximum air-gap to minimum air-gap is eventually determined to be 3.2. The results of simulation and experiment show that, for the specified rotation direction, the distortion of air-gap magnetic density and back electromotive force (back-EMF) caused by armature reaction can be significantly suppressed by the determined asymmetric structure, hence the torque ripple and iron loss are reduced by 70.66% and 20.9% under rated load, respectively. Meanwhile, the proposed motor can provide a wide speed range and superior speed control performance, thus, verifying the validity and feasibility of the proposed asymmetric eccentric air-gap structure.     

Radial Force Analytic Modeling for a Novel Bearingless Switched Reluctance Motor When Considering Rotor Eccentricity

Abstract—Analytic modeling of radial forces is proposed for the novel bearingless switched reluctance motor, where the rotor eccentricity is taken into account. The novel bearingless switched reluctance motor's model is never disclosed, even though there are many advantages, such as fewer suspension windings and simpler control circuit and algorithm, when compared to the conventional bearingless switched reluctance motor. The analytic model of radial forces is very important to achieve this new bearingless switched reluctance motor's suspension control. The rotor eccentricity is a key cause to affect the radial forces. This article calculates the air-gap permeances through considering rotor eccentricity. The self-inductance and mutual-inductance expressions of the motor torque windings and the suspension windings are derived by using the magnetic equivalent circuit method. The derived radial force model discloses the effects of winding currents, rotor position angle, and rotor eccentricity displacement. The finite-element analysis based results verify the built model.     

TESTS OF AN AXIAL AIR-GAP VARIABLE RELUCTANCE MOTOR SUPPLIED BY A SOLID-STATE CONVERTER

ABSTRACT

An axial air-gap variable reluctance motor with a mobile disc between two stationary discs is tested in the 0 to 400 Hz frequency range. The machine is combined in succession with two converters of original design. The results are presented in the flux/ampere-turns plane, with physically illustrates the intrinsic possibilities of this type of motor. Experiments is conducted with two air-gap values (1 mm and 0.6 mm), this helping to estimate accurately the performance gains achieved by reducing the air-gap. Emphasis is placed on the need to saturate the iron in the discs completely.     

Development and characteristics of servomotor for use under high temperature and radiation flux conditions

Recently, robots have been required to inspect the insides of nuclear reactors under high temperature and radiation flux conditions. In a FBR (fast breeder reactor), the viewing system of the robot is particularly important because the reactor vessel of the FBR is filled with opaque liquid sodium. To drive this robot, servomotors must meet special requirements. At temperatures above 220°C, the integrity of organic materials cannot be maintained for long periods. In addition, the air-gap length of the motor varies, because metals expand at high temperatures. Thus, the characteristics of induction motors with an air-gap length of 0.2–0.4 mm may vary. Furthermore, the rotor may come into contact with the stator. In this paper, a newly developed permanent magnet motor which can withstand high temperatures and radiation is presented, and the characteristics of the rotor at high temperatures are discussed. Coils for winding ceramic magnetic wires are installed in the stator and Sm₂Co₁₇ permanent magnets are embedded in the rotor yoke. This motor is suitable for use at up to 400°C due to the use of inorganic materials in it. In addition, the permanent magnet motor can incorporate a long air-gap length, which has little effect on the characteristics of the motor. The test results show that the motor has excellent characteristics at high temperature. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(4): 52–65, 1997     

基于定子绕组并联支路环流特性的发电机故障识别方法

分析了发电机气隙磁势、磁导、磁密、定子绕组两条并联支路的感应电势和电路方程,得到定 子绕组并联支路间的电压差表达式。通过分析正常及故障运行时各参数的变化得到了并联支路电 压差和环流特性,理想电机在正常运行时不存在电压差和环流,而转子绕组短路故障将引起二次谐 波环流,定子绕组短路、定转子气隙静偏心、气隙动偏心故障将引起基波环流。由于不同故障引起 的环流特性存在差别,提出了基于定子绕组并联支路环流特性的发电机故障识别方法,并实测了 SDF-9型故障模拟发电机正常及故障运行时的环流信号,与理论分析结果基本吻合。     

An induction motor model with deep-bar effect and leakage inductance saturation

Contents A two-phase dynamic induction motor model is derived which includes the effects of rotor bar eddy currents and leakage inductance saturation. The model is based on approximate analysis of the air-gap and slot electromagnetic fields which leads directly to lumped circuit equations. New expressions are given for the variation of the zig-zag and slot leakage inductance with saturation. — The model is applied to the calculation of both steady state and dynamic characteristics for a large induction motor.

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Ein Modell des Asynchronmotors mit Hochstabläufer-Effekt und Sättigung der Streuinduktivität

Übersicht Es wird ein zweisträngiges Modell eines Asynchronmotors abgeleitet, das Wirbelströme in den Läuferstäben und die Sättigung der Streuinduktivität berücksichtigt. Grundlage des Modells ist eine angenäherte Analyse der Felder im Luftspalt und in den Nuten, die direkt auf Gleichungen mit konzentrierten Elementen führt. Es werden neue Ausdrücke für die Abhängigkeit der doppeltverketteten und der Nutstreuung von der Sättigung angegeben. Das Modell wird für die Berechnung stationärer und dynamischer Vorgänge bei einem großen Asynchronmotor angewendet.

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List of Symbols A magnetic vector potential - B flux density - G describing function - g air-gap length - H magnetic field intensity - I _Om rotor saturation current - I _r rotor current matrix - l _r ^j current in thejth rotor slot - l _rm amplitude of the fundamental ofI _bir ^j distribution - I _rr rotor harmonic conceptual current matrix - I _s stator current matrix - I _ss stator harmonic conceptual current matrix - i _mne m, nth modal eddy current in thejth rotor slot - i _nb nth harmonic conceptual current at the interface betweenjth rotor slot and slot neck regions - i _n ^rj nth harmonic conceptual current at the opening of thejth rotor slot - i _n ^sj nth harmonic conceptual current at the opening of thejth stator slot - i _Ob rotor zero order conceptual current matrix - i _Oi ^j conceptual current at thejth rotor slot due to daturation of the tooth tips - K _nw nth harmonic winding distribution factor effective length of the motor - L _nc self inductance of the eddy current modei _One ^j - L _r rotor inductance matrix - L _s stator inductance matrix - P _p pole pitch - M _ne mutual inductance betweeni _One ^j andI _r ^j and rotor modal eddy currents - M _ri mutual inductance matrix between rotor winding and rotor conceptual winding due to saturation of the tooth tips - M _rr mutual inductance matrix between rotor winding and rotor conceptual winding - M _rss mutual inductance matrix between rotor winding and stator conceptual winding - M _si mutual inductance matrix between stator winding and rotor conceptual winding due to saturation of the rotor tooth tips - M _sr mutual inductance matrix between stator and rotor windings - M _srr mutual inductance matrix between stator winding and rotor conceptual winding - M _ss mutual inductance matrix between stator winding and stator conceptual winding - N ₁,N ₂ number of stator and rotor slots - R _ne resistance of eddy current modei _One ^j - R _r rotor resistance matrix - R _s stator resistance matrix - s ₁,d ₁ dimensions of a stator slot - s ₂,d ₂ rotor slot opening and rotor slot neck height - s _b ,d _b dimensions of a rotor bar - s _p slot pitch - N _c number of turns per slot - U _s applied voltage matrix - q number of slots per pole phase group - rotor flux linkage matrix - y_s stator flux linkage matrix - , inductance coefficients - O angular position - conductivity of rotor bars - eigenvalues - resistivity of rotor bars     

定子绕组匝间短路对发电机定转子径向振动特性的影响

分析了定子绕组匝间短路故障时发电机定转子径向振动特性，首先分析定子绕组匝间短路后气隙磁场变化特征，计算得到气隙磁密、气隙磁导和气隙磁场能量的表达式，然后得到作用于转子的不平衡电磁力特性和作用于定子的脉振电磁力特性，最终得到定转子径向振动特征。并实测了MJF-30-6型模拟发电机定子绕组匝间短路时定转子径向振动信号，与理论分析结果基本吻合。另一方面也揭示了诸如绕组短路的电气故障与发电机机械振动之间的关系，指出了发电机径向振动特征与发电机电参数一样，也可作为诊断发电机绕组故障的依据。     

MAGNETIC CIRCUIT STUDIES FOR AN AXIAL-GAP RELUCTANCE MOTOR

ABSTRACT

The analysis of the magnetic circuit of an axial air-gap, battery-excited reluctance motor is presented. Permeance coefficients from which machine inductance can be calculated are derived. Inductance values calculated from these permeance coefficients are compared with values determined by magnetic analogs and by studies of air gap magnetic potential distribution using relaxation techniques and the Finite Element technique.     

A NOVEL MODEL FOR SINGLE-FRAME CASCADED INDUCTION MACHINE HAVING A MULTICIRCUIT ROTOR WINDING

ABSTRACT

This paper presents a new steady-state circuit model for a Single-Frame Cascaded Induction Machine (SFCIM) having a multicircuit single-layer bar rotor winding. The rotor winding, which consists of a large number of mostly mutually coupled circuits is complex. An impedance matrix containing parameters which can be calculated relatively simply, is used to represent the coupling of the rotor winding to stator windings. Theoretical results obtained using this model are presented, together with experimental results.     

SPLIT-WINDING STARTING OF A SINGLE-PHASE INDUCTION MOTOR

Abstract

Results of investigation of starting a single-phase induction motor having a single stator winding and using normal stator and rotor punchings are presented in this paper. Theoretical and experimental studies show that the motor requires less copper for its stator winding compared to a split-phase motor and the overall starting performance is very satisfactory.     

基于气隙基波磁场交流电机电感参数的统一计算公式

在考虑气隙基波磁动势产生基波磁通密度的情况下,推导了计算交流电机电感参数的统一公式。根据等效整距集中绕组与实际绕组产生相等基波磁动势的原则,给出了实际定子绕组与转子绕组的总有效匝数表达式。分别以三相同步电机与十二相同步电机为例,说明了统一计算公式的具体应用过程,并证明了公式的准确性和有效性。     

开关功率变换器中高频电感器的分析与设计

对高频率和大电流的开关功率变换器,电感器损耗对温升及变换器效率指标具有重要影响.通过高频电感器线圈损耗机制的深入分析,对铜箔线圈以及里兹线线圈进行了比较,提出了线圈避开气隙扩散磁通的设计思想和原则.研究了基于功率铁氧体材料性能因素(PF)指标的铁芯材料选用依据.改进、设计了一种高频串联谐振型逆变器的谐振电感器,在1 kVA容量时,使逆变器整机效率提高了4%.     

ANALYSIS OF THE M/N WINDING ASYNCHRONOUS MACHINE WITH SPACE HARMONICS USING SYMMETRICAL COMPONENTS

ABSTRACT

This paper is concerned with the analysis of the asynchronous. machines with m symmetrical stator windings and a rotor of cage type which consists of n symmetrically distributed bars. The analysis is performed in the presence of space harmonics. Considering the relation between any sequence of symmetrical components related to unbalanced voltage supply, the possibly established space harmonics can be assigned. The m/n wielding machine voltage equations are presented in phase coordinate form in order to apply a transformation by symmetrical components. Sufficient conditions are presented in order to express these equations in the form of linear differential equations with constant coefficients. The suggested method is able to include large numbers of space harmonics. The transformation with the help of symmetrical components here will divide the complete set into n separate subsets when it is applied to the rotor quantities. The equivalent symmetrical component model of the m/n winding machine will make the stator/rotor space harmonics interactions more understandable.

It is also possible to discuss the problem of obtaining linear voltage differential equations by simpler method.     

Basic principles and characteristics of hybrid excitation synchronous machine

Permanent magnet type synchronous machines have been widely used for industrial applications. It is commonly known that they are operated at high efficiency since no excitation input is required. However, it is difficult to control the air-gap magnetic flux, because the magnetic flux is determined by the property of the permanent magnet and approximately kept constant. On the other hand, synchronous machines with the field winding make it easy to control the air-gap magnetic flux. But the copper loss of the field winding becomes large at the rated load. In order to realize the magnetic flux control easily and improve the performance of the conventional synchronous machine, we propose a hybrid excitation type synchronous machine (HSY) with the permanent magnets and the field winding. Advantages of HSY are (1) it has no brushes (maintenance free), (2) required excitation input is small (high efficiency), (3) it is easy to get a sufficient magnetic flux control, and others. Therefore, HSY has a great possibility of use for various applications. In this paper, basic principles and characteristics of HSY are mainly discussed and made clear.