ANALYSIS OF THE INTERFERENCE SYNCHRONOUS MACHINE

ABSTRACT

Interference synchronous machines operate at different speeds of the fundamental air gap field and of the rotor, because the fundamental permeance wave is produced by interference of open stator and rotor slots the numbers of which being slightly different. In the literature different names are used for this remarkable electrical machine (“Synchronous inductor motor”, “Vernier reluctance motor”). Interference synchronous machines are used as homopolar frequency generators with an axial field coil, as continuous running reluctance motors and as single- or double, - stack step motors with an axial permanent magnet.

In this paper the field of the interference synchronous machine is analysed by field wave theory. Speed,phase angle and length of the largest field waves reveal how synchronous and cogging torques are produced. Voltage and torque equations are derived by axis theory from the simplest model that is possible with five rotor teeth. The theory is applied on a fifty rotor teeth double-stack step motor. The inductances are determined by a difference method field calculation. The torque of the motor is then calculated and compared with measured values.     

Computer-Aided Analysis of a Converter-Fed Saturated Synchronous Motor Drive

ABSTRACT

A method of numerical simulation for evaluation of the performances of a variable speed synchronous motor drive is developed. The machine has rotor saliency with armature and damper windings. Magnetic saturation in both d and q axes are also taken into consideration. The model is focused specially for analysis of a self-controlled reluctance motor drive fed either by voltage source inverter or current commutated inverter. The computer solution permits accurate calculation of current, voltage, and torque waveforms. Sample calculations for highly saturated converter-fed reluctance motor drive are presented including comparison with practical tests.     

Performance of PM-assisted synchronous reluctance motor forhigh-efficiency and wide constant-power operation

This paper examines the design and the performances of a permanent-magnet assisted synchronous reluctance motor (PMASRM) for wide constant-power operation. The effects of properly adding magnets into the rotor of a synchronous reluctance motor are examined by several experimental results and analyses on the prototype machines. The proposed machine can offer a large constant-power speed range, high-efficiency and high-power-factor operation in comparison to the complete synchronous reluctance motor. It was shown that the problems such as the decrease of efficiency at light-loads and the uncontrolled generator mode operation, which occur in the high-speed flux-weakening operation of the conventional PM motor drives, can be eliminated in the PM-assisted synchronous reluctance motor     

Efficiency of Small Homopolar Synchronous Motors at High Speeds

Summary

In this paper, some efforts have been made to relate the efficiency of homopolar synchronous machines of the ‘reluctance rotor’ type to their design parameters. Particularly emphasized are the influences of the rotor pole shape, supply frequency and stator slotting. The indications given are based on results of numerous experiments on to prototype motors of a special design with a limited active length. From these results it is evident that only under exceptional circumstances, when despite high-speed operation excessive windage losses can be avoided, this kind of motor may be interesting for practical application.     

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     

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.     

Field-weakening performance of interior permanent-magnet motors

This paper compares the field-weakening performance under rated and overload conditions of synchronous reluctance and interior permanent-magnet motors against that of a baseline 2.2-kW induction machine. Four prototype rotors based on axially laminated and multiple-barrier designs were built and tested in the same induction machine stator. Field-weakening performance was estimated based on 50-Hz load tests at reduced voltage. It was found that the performance of the axially laminated synchronous reluctance machine was comparable with the induction machine while the interior permanent-magnet motors offered significantly better output power above rated speed. The multiple-barrier interior permanent-magnet motor design gave the most promising field-weakening performance.     

同步磁阻电机作为机床主轴驱动的研究

对现有的交流电机主轴驱动系统进行了概述,提出可用同步磁阻电机作为机床的主轴驱动,并且比较了各种电机主轴驱动的优缺点,指出同步磁阻电机的优势。分析了同步磁阻电机作为主轴驱动的控制方法以及弱磁控制方法,并仿真比较其与永磁同步电机的转矩特性,阐明同步磁阻电机是机床主轴驱动的理想机种。     

A Hybrid Interior Rotor High-performance Line Start Permanent Magnet Synchronous Motor

Abstract—This article describes the development of a line start permanent magnet synchronous motor with a rotor containing interior mounted magnets. The rotor is a hybrid of both circumferentially as well as radially magnetized magnets arranged so it produces consequent poles. Steady-state and transient performances of the line start permanent magnet synchronous motors have been analyzed by using time-stepping finite-element analysis. Simulation results show that the optimum performance of the rotor is achieved for a specific magnet volume, a substantial improvement on performances of all such rotors reported so far (based on the detailed study of all these rotor types). The hybrid rotor has improved the synchronous performance of the machine without degrading its starting characteristics when compared with an equivalent induction motor. Two experimental prototypes of the proposed design have been built in the laboratory, and their performances have been compared with the performance of a conventional line start permanent magnet synchronous motor having only circumferentially magnetized magnets in its rotor, as well as that of a standard induction motor of the same frame size and physical dimensions. The results indicate that the proposed hybrid interior rotor significantly improves machine performance.     

EFFECT OF PARAMETER CHANGES ON THE PERFORMANCE OF SOLID ROTOR THREE-PHASE RELUCTANCE MOTORS

ABSTRACT

An adequate understanding of the close relation existing between performance characteristics and machine parameters is essential for designing any reluctance motor.

The present paper deals mainly with how the steady-state stability of small solid rotor three-phase reluctance motors is affected by the machine parameters. The effects of certain typical machine parameters have been quantitatively demonstrated, which may be instrumental in designing the motor.

To confirm the results obtained, a comparative review of calculated and experimental values is also presented for a number of different machines.     

Parameter Sensitivity Analysis for Line-Start Permanent Magnet Motors

ABSTRACT

A comprehensive study of the parameter sensitivity on both the synchronous and asynchronous performances of permanent magnet machines is presented. Based on the 2-axis theory for permanent magnet motor, performance equations are derived In terms of normalized machine parameters. Such an analysis can be used successfully in design optimization of permanent magnet machines.

A normalized power equation for evaluating the steady-state stability limits of such type of motor is also given. Simulation results obtained are confirmed with experimental results using a number of different rotor designs. Useful conclusions have been provided, which are considered to be a good aid for designing any permanent magnet motor.     

Emerging Electric Machines with Axially Laminated Anisotropic Rotors: A Review

ABSTRACT

This paper presents a class of multiphase electric machines with axially laminated anisotropic (ALA( passive rotors. Unipolar, two-level bipolar, and sinusoidal current modes are identified. The reluctance variation in ALA rotor is computed for a wide range of airgaps and pole pitches. High ratios of inductances along d and q axes yield high torque densities. Special attention is paid to the sinusoidal current mode through a quantitative comparison with the induction and PM synchronous counterparts with the same stator. It is demonstrated that the ALA rotor sinusoidal current synchronous motor is superior in all respects to the induction motor and almost equals the performance (torque density, efficiency, power factor( the PM synchronous motor.     

CORRESPONDENCE: EXPERIMENTAL STUDIES ON POLE CHANGING SYNCHRONOUS INDUCTION MOTORS

ABSTRACT

Experimental studies on pole changing synchronous Induction motor (S.I.M) reveal that a second synchronous operation oan be had in close ratio cases. Although only a second induction is possible in a vide ratio two speed S.I.M, it has superior characteristics over a similar cage rotor machine.     

COMBINED FINITE ELEMENT AND ANALYTICAL METHODS FOR ROTOR DESIGN OF PERMANENT MAGNET SYNCHRONOUS MOTORS

ABSTRACT

While design procedures for conventional induction and synchronous machines are now mature and constrained by frame sizes and standards, there are opportunities to use modem CAD techniques to exploit the unique capabilities and characteristics of permanent magnet synchronous motors (PMSM). This paper presents a design methodology involving the use of an analytical model based on generalized machine theory, complemented by finite element analysis. The synergistic interaction of these two methods allows an engineer to design a PMSM to specific requirements with confidence. The effects of machine airgap and of the span angle and thickness of the permanent magnets are evaluated. A set of design specifications and a goodness function are established to select the preferred rotor geometry for a 30 hp prototype permanent magnet synchronous motor.     

THE TRANSFER-FIELD ELECTRIC MACHINE

ABSTRACT

A new kind of brushless reluctance-effect machine was described recently. This machine differs from conventional reluctance and inductor-type machines in having a segmented rotor. There is also a further difference in that there is a translation (or rotation) of the active air-gap flux in addition to the usual pulsation associated with the other reluctance-effect types. Thus, the machine is partly an electromagnetic machine and partly a magnetic machine. In the basic machine armature reaction effects pose a serious problem. It is shown in this paper how these effects may be eliminated, and it is also shown that the basic machine is the primitive form of a more general class named transfer-field machines. Like other inductor/reluctance types the machine will operate satisfactorily in the synchronous mode, but unlike them it will also operate in the asynchronous and dc modes. Some preliminary experimental results are also reported.     

Analysis of a new variable-speed singly salient reluctance motorutilizing only two transistor switches

A novel type of two-phase synchronous reluctance motor drive is introduced and analyzed. Since the currents in the phases are unidirectional rather than bidirectional, the associated power converter requires only two transistors and two feedback diodes. It is demonstrated by the finite-element method of analysis that with the same amount of active copper and under the same rated power output, the copper losses of this machine can be reduced to 75% of that of the equivalent switched reluctance motor     

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.     

Performance Calculations of a Reluctance Motor Drive by dq Harmonlc Balance

A method of analyzing the constant speed steady-state performance of a reluctance motor fed from voltages of an arbitrary waveform is presented. The solution is obtained directly from Park's equations by a time-domain harmonic balancing approach related to the method of multiple reference frames. Both synchronous and asynchronous operation can be obtained from the same theory. The method is readily extended to incorporate any type of synchronous machine. Harmonic balancing is applied to the performance calculations of a reluctance motor supplied by a square wave voltage source inverter. Comparisons are made with more conventional approaches.     

Identification of machine parameters of a synchronous motor

This paper presents a method for estimating the machine parameters of a synchronous motor. The presented method is equally applicable for a wound field synchronous motor, synchronous reluctance motor, or permanent magnet (PM) synchronous motor, both the interior and surface-mount types. The method works particularly well for machines having a significant amount of space harmonics, such as synchronous reluctance and interior PM (IPM) machines, where the harmonics are predominantly the slot harmonics. It is also well suited for surface PM machines operating under saturation, where the harmonics are saturation-induced. The presence of these harmonics makes the parameter identification difficult. Most of the methods presented so far in the literature have failed to properly identify machine parameters in the presence of space harmonics. In this paper, the machine parameters, identified by using a proposed algorithm, are compared with the finite element and the experimental results to demonstrate the effectiveness of the presented method. Both interior PM and surface PM machines are considered.     

On-line efficiency optimization of a synchronous reluctance motor

This paper deals with an on-line optimum-efficiency control of a synchronous reluctance motor drive. The input power minimization control is implemented with a search controller using Fibonacci search algorithm. It searches the optimal reference value of the d-axis stator current for which the input power is minimum. The input power is calculated from the measured dc-bus current and dc-bus voltage of the inverter. A rotor-oriented vector control of the synchronous reluctance machine with the optimization efficiency controller is achieved with a DSP board (TMS302C31). Experimental results are presented to validate the proposed control methods. It is shown that stability problems can appear during the search process.