HARMONIC FIELDS IN PHASE-SHIFT-MODIFIED POLE-CHANGING WINDINGS FOR POLYPHASE INDUCTION MOTORS

ABSTRACT

A recent article proposed a phase-shift-modification technique for developing two-speed pole-changing windings for polyphase induction motors. In this article the author investigates the harmonic mmf content of three of the windings proposed, making use of a procedure developed and published over a dozen years ago. The results are compared with the results of similar analyses on commonly used fractional-slot least-common-multiple windings; they are also compared with the harmonics in a pole-amplitude-modulated arrangement. This analysis reveals the existence of very serious harmonic mmfs in at least two of the three phase-shift-modified arrangements proposed in the recent article, and shows the third arrangement to be much better, though still somewhat inferior to the other windings analyzed.     

HIGH-EFFICIENCY SINGLE-PHASE SEMIHEX™ MOTORS

ABSTRACT

These single-phase motors can now have the high efficiency of 3-phase motors. They are a three-phase construction with a SEMIHEX? connection of the windings to two run capacitors. Nearly all single-phase products, and particularly air conditioners, can use these high-efficiency motors. These can save billions of dollars for the consumers. The single-phase winding currents at full load are the same as if the motors were connected to a 3-phase source. The single-phase full-load efficiencies are the same high efficiencies as the 3-phase motor on a three-phase supply. The power line sees a leading power factor of approximately 87%. The single-phase line current is approximately 1.7 times what the three-phase line current would be. The line starting current is unity power factor and is less than three times the full-load current for motors between 10-HP and 100-HP. Single-phase motors as large as 100 horsepower are readily built at low cost.     

OBSERVATIONS ON THE DESIGN OF DISTRIBUTED ARMATURE WINDING BY POLY PHASE SYMMETRISATION

ABSTRACT

The generalised process of designing distributed poly-phase armature windings by the technique of symmetrization offers special advantages in developing dedicated machines for operation with non-sinusoidal supplies.

Principles of symmetrization have been reviewed with special reference to 3-phase windings and important rules governing the applications of the process have been enumerated, both with reference to single-speed balanced and unbalanced windings as well as multi-speed windings.

Although such special windings in general, have wider harmonic spectra compared to standard designs, a judicious selection of symmetrised windings can, in fact prove beneficial in specific cases. The paper attempts to lay down the procedure for systematic design of 3-phase symmetrised windings.     

NEW 4/6-POLE RELUCTANCE MOTORS

ABSTRACT

A new type of reluctance-rotor having four asymmetrical segments is introduced and fully explored for 4/6-pole operation. This rotor is derived from the novel magnetic circuits recently described [7] and analysed [8] by the present authors. Predicted variations of synchronous performance with certain important machine-parameters are given, and the new rotors are shown to be superior to earlier designs for this speed ratio, one with symmetrical segments [4], and one with salient-poles [5J. Test results of two motors for constant torque and constant horsepower applications employing P.A.M. stator windings are presented, together with some experimental verification of theory. The new motors are believed to have the potential for several industrial applications.     

APPLICATION OF INVERSE TRANSFORMATION TECHNIQUE TO 3-PHASE POLE-CHANGING WINDINGS

ABSTRACT

The inverse d-q transformation is used to develop pole-changing 3-phase induction motors from change-pole 2-phase ones. Transformation procedures, common features of the original 2-phase and derived 3-phase windings, basic differences between derived and conventional 3-phase windings together with their limitations are discussed in detail. Single winding change pole arrangements for 3-phase machines are derived from 2-phase ones. In addition, a mathematical model is presented to take satisfactorily into account the effects of unbalanced impedances and multi harmonic interactions. Tests conducted both in 2 and 3-phase operations on a 10/6 change-pole machine are reported. The nature of agreement between the computed and experimental results validates the transformation technique and also the mathematical model used in the process.     

CAGELESS RELUCTANCE MOTOR: A NEW IMPROVEMENT IN DESIGN

ABSTRACT

Recently, reluctance motors found numerous fields of applications. This is mainly owed to its simplicity in construction, robustness, and speed constancy. However, the first advantage is partially offset by the fact that extra starting windings should be fitted in the rotor body to achieve motor's self starting and synchronization.

This paper presents an improved design of reluctance rotors in which starting is achieved with no need for extra starting cage windings. Starting in this type is achieved by virtue of the induced currents in the rotor's solid body.

To evaluate the new type's performance, a comparison is done and presented between this type and conventional one having the same particulars. Theoretical analysis is also done to study the effect of different rotor parameters such as inter-stacks shift angle and pole arc/pole pitch ratio on this developed type's performance. Validity of the proposed analysis is checked by experimental results.

It is shown that the merit of self starting and synchronisation is achieved on the expense of synchronous performance of this type of motors. Consequently, it becomes then a matter of compromise between self starting and synchronisation requirements and the synchronous running performance such that this new design can be successfully employed.     

MAGNETIC FIELDS AND INDUCTANCES OF HELICAL WINDINGS WITH 120° PHASEBANDS

ABSTRACT

In the development of superconducting a.c. generators the essential air-cored nature of the generator, and the large power output per unit length, suggests that conventional armature windings may not necessarily be the most suitable. One possible alternative is the helical armature winding (3) - (8) and has been proposed both as a means of obtaining a uniformly supported armature structure and for generating at transmission line voltages.

This paper discusses the peculiarities of helical windings, and in particular those with 60 and 120° phase-bands. Magnetic field and inductance measurements are made on a three phase model with a phase spread of 120° and compared with calculated values using a previously published theory (4). Computed and measured values of synchronous inductance agree to within 1%.     

AN ANALYSIS OF SHADED POLE INDUCTION MOTORS WITH INCREASED STARTING TORQUE

ABSTRACT

A method of analysis of shaded pole induction motors with ununiform airgap is described. For the analysis, a dq model of a generalised machine theory with any number of stator windings arranged in an arbitrary way on the stator and ununiform airgap is chosen. The analysis involves resolution into a harmonic series, together with complex matrix inversion. Results of computational study of the effect of changes of airgap profile on the performance characteristics are presented. It is shown that by increasing the airgap under the part of a pole which la opposite to the shading coils, an increased starting torque can be obtained.     

六相双Y移30°绕组结构及其应用优势

随着电力电子技术的迅速发展,利用先进的控制技术可以方便的将三相电源变多相电源,因此多相电机得到了迅速的发展。六相双Y移30°绕组是多相绕组中应用较多,具有很好发展前景的一种绕组,交流电机采用六相双Y移30°绕组是减少高次谐波、提高电机效率以及提高电机极限容量的有效措施。介绍了六相双Y移30°绕组的构成理论,对其磁势谐波进行了谐波分析,并对这种绕组的优点进行了简单分析叙述。     

双绕组电机在电力系统中的发展

与传统笼型感应电机相比，双绕组电机具有降低电机谐波损耗、杂散损耗及转矩脉动的性能。综述了双绕组电机的研究状况，预测了双绕组电机的应用前景。     

A Method for Design of Two-Speed Shunted Capacitor Motor

ABSTRACT

Equations for predioting the performance of 2–speed shunted capacitor motors with arbitrary arrangements of primary windings are developed using 2–phase symmetrical oomponent method. Further, from the standpoint of motor designers, a method for selecting turns ratio and capacitor of shunted capacitor motor is proposed. This method is based on the equal capacitive volt-amperes method. The high speed and low speed performance of the motor obtained by this method are studied. The high speed performance is found to be almost always the same as the performance in balanced operation, and the low speed performance is defined in connection with the turns ratio and the capacitance chosen.     

五相混合式步进电动机四步一个循环的轻重步现象

我国从１９８７年开始生产五相混合式步进电动机以来，就发现在半步方式工作时有四步一个循环的走步不均匀现象。本文给出了较完善的分析和说明，实验校核了分析的正确性，确定表明这种现象是特定的绕组联接和功率驱动方式的产物，也就是说采取不同的功率驱动电路和绕组联接，不仅影响电动机的转矩性能指标，而且对走步的均匀性也有一定的影响。     

A Unique Solution to Improving Motor Winding Life in Medium-Voltage Motors

It has been recognized for years that electrical motors installed in petrochemical plants require protection from condensation. Papers have compared different methods of preventing condensation from collecting in 600-V motor windings. These papers covered the advantages of directly heating the motor windings by introducing a low-voltage ac or dc source to the windings when the motor is not running. Their conclusion was that low-voltage heating. is the most practical solution to motor moisture problems since the heat is evenly distributed throughout the stator windings and does not cause hot spots in the windings as conventional motor heaters can. Many installations in recent years have proven the reliability of this low-voltage application to windings. A case history is given of retrofitting a newly developed motor windings heater to an existing 5000- hp 2300-V synchronous motor that has had numerous winding failures due to moisture. The installation is at ARCO Chemical Company's Port Arthur, TX, plant.     

OPTIMIZATION OF DUAL SPEED INDUCTION MOTORS

ABSTRACT

Design optimization of single-winding dual speed and double-winding dual-speed three phase induction motors is attempted. The choice of independent variables and the specification of the performance requirements for these two types of motors are discussed. The formation of an objective function end the various steps involved in the minimization process are explained. It has been shown that comprehensive computer programs can be developed to design optimum dual speed motors of any pole ratio with any stator coil span and winding connection.     

Torque and suspension force in a bearingless switched reluctance motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. The bearingless switched reluctance motors are characterized by integration of switched reluctance motors and magnetic bearings. These motors have two kinds of stator windings composed of motor main windings and suspension windings in the same stator in order to produce suspension force that can realize rotor shaft suspension without mechanical contacts or lubrication. For successful stable operation, accurate theoretical formulas of instantaneous torque and suspension force are necessary to a rotational speed controller and a rotor radial position controller. This paper derives the theoretical formulas of the instantaneous torque and the suspension force from an assumption of simple permeance distribution. This derivation process makes an assumption that fringing fluxes are distributed on elliptical lines. It is shown with experimental results that the derived theoretical formulas are very accurate in terms of practical application. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 72–82, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20157     

PERFORMANCE ANALYSIS OF A HIGH STARTING TORQUE SINGLE-PHASE INDUCTION MOTOR

ABSTRACT

The objective of the work described is to make an assessment of the possible use of three-phase induction motor working as a single-phase motor. The analysis is performed on the proposed winding arrangement, introduced previously by same authors. The analysis includes all motor windings, whereas the conventional analysis is performed on the running winding only. The motor windings are analyzed through the stationary direct and quadrature axes. The magnetic field and E.M.F's of the motor are studied at starting, run-up and running operation. Hence, d-q axis equivalent circuits are deduced to represent the motor at different modes of operation, taking into consideration the core losses and sturation effects. Prediction of the run-up and running characteristics of the motor under investigation is achieved by solving the equations of equivalnet circuits in a simple manner. The predicted results are compared with the releavant experimental results. Good agreement has been achieved, and this confirms the validity of proposed analysis.     

120°相带环形绕组直驱永磁同步电机性能分析

基于相同电负荷、磁负荷及等永磁体用量的设计原则,建立了不同绕组结构的传统直驱永磁同步电机(DDPMSM)、传统环形绕组DDPMSM和120°相带环形绕组DDPMSM的有限元模型.分析了空载运行时3种电机的磁场分布、气隙磁密和反电势,对比了负载运行时3种电机的输出转矩、效率及功率因数等性能参数.制造了一台120°相带环形...     

无刷绕线型感应电动机的研究与仿真

无刷绕线型感应电动机采用谐波起动的原理对电机的绕组进行独特的设计,使其具有高的起动性能和无刷的转子结构。介绍了这种电动机的基本原理,给出了一种绕组设计方案,研究出了电机在M-T坐标系下的数学模型,并在此基础上建立了电机的Matlab/Simulink仿真模型,通过仿真实例验证了该电机的优越性。     

PWM INVERTER FED INDUCTION MOTORS LOSSES EVALUATION

ABSTRACT

In this paper the authors deal with the problems concerning the steady state losses evaluation in medium power industrial induction motors supplied by PWM inverter. They present a method based on the no-load and short circuit tests. This technique seems to be very useful for the good obtained results and because it is quite similar to the standard no-load and short circuit tests used with sinusoidal voltage supply.

The method is based on some simple hypothesis that have been verified during the experimental tests by means of mathematical models. As a consequence, it is possible to compare the no-load and the short circuit tests under sinusoidal and PWM inverter supply considering the same rms fundamental voltage.

The method has been applied to a 7.5 kW induction motor supplied by a prototype PWM Voltage Source Inverter (VSI) modulated with a ramp comparison technique at a 1 kHz switching frequency.

The obtained results could be utilized in order to define some design criteria and the derating for standard induction motors supplied by PWM inverters.     

AXIAL FLUX WHEEL MACHINES FOR ELECTRIC VEHICLES

ABSTRACT

Several possible solutions for axial flux wheel motor drives for Electric Vehicles (EVs) are invesligated. As a case study, a small electric city car has been chosen and a 10 kW motor for each wheel has been selected for the comparison between the different motors types. Among die different solutions, die axial flux interior PM motors seem to be the best compromise in terms of efficiency, weight, compactness and capability characteristics.