SYNCHRONOUS STARTING OF SYNCHRONOUS MACHINE

ABSTRACT

Synchronous starting is one of the methods for starting large synchronous motors by small synchronous generators. The equations for Concordia's interlocked generator-motor block logic for synchronous starting are derived in detail. The equations for software implementation including saturation and motor friction torque are presented. Alternative procedure, to overcome numerical differentiation in motor equations, is suggested. Simulation results based on Software developed are given.     

TORQUE PRODUCTION IN ac MOTORS WITH CONSTANT CURRENT SUPPLY

ABSTRACT

Basic theory is presented concerning the production of torque in synchronous motors and induction motors under conditions of constant current supply. Simple methods are described for treating the effects of magnetic saturation, which are important at high currents. It is shown that, for a given stator current, a synchronous motor produces more torque than an induction motor, albeit with higher air-gap flux. Examples illustrate the variation, due to saturation, of the optimum torque angle of synchronous motors with cylindrical and salient rotors.     

TORQUE CHARACTERISTICS OF A SELF-CONTROLLED SYNCHRONOUS MOTOR

ABSTRACT

This paper presents a study of the torque characteristics of a self-controlled synchronous motor drive in which motor terminal voltages are used for inverter synchronization. Torque control techniques for normal operation and for starting are considered. A control strategy which optimizes the motor power factor and torque is studied. Experimental results are given.     

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.     

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.     

COMMUTATION TRANSIENTS IN SELF-CONTROLLED SYNCHRONOUS MACHINES CONNECTED TO D.C. NETWORKS

ABSTRACT

In this paper the commutation phenomenon in a synchronous machine (generator or motor) associated with a thyristor bridge is studied. The transient analysis of the different currents in the different windings is done for a salient pole synchronous machine with damper windings. The different expressions are given in terms of the classical machine reactances and time constants which can be directly measured or furnished by the manufacturer. Comparison between theoretical and practical results are given.     

OPTIMAL WINDING DESIGN OF A PERMANENT MAGNET MOTOR FOR SELF-CONTROLLED INVERTER OPERATION

ABSTRACT

This paper describes a novel design of the three-phase synchronous motor which is tailored to match the operational characteristics of the self-controlled inverter. The design is based on a square waveform distribution of the rotor radial B-fields and square waveform distributions of the winding densities of the stator phases around the periphery of the airgap. The motoring torque has minimal time harmonics. The design achieves a maximum power density for the frame size of the motor. It is ideally suited for permanent magnet synchronous motors.     

MICROCOMPUTER BASED EFFICIENT AUTOSYNCHRONOUS MOTOR DRIVE

ABSTRACT

The paper presents the development of a microcomputer based digital control system for the current source load-commutated inverter fed synchronous motor drive. The control system comprised two loops: (i) Fast acting dynamic speed and torque angle control loop to ensure the self synchronous operation of the drive system, disturbance rejection and robustness of the complete motor drive system. (ii) Slow acting quasi steady-state efficiency maximization loop that ensures that the drive load is met at minimum source power input.     

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.     

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.     

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.     

AN EXPERIMENTAL STUDY OF A HOMOPOLAR LINEAR SYNCHRONOUS MOTOR

Abstract

This paper presents some experimental results obtained from a small homo-polar linear synchronous motor which has been tested on the two-metre test wheel facility at the University of Toronto. The primary of the motor has both armature and field windings while the secondary consists of alternately-placed solid iron poles on the wheel rim. A short three-pole primary has been used so that end effects are accentuated. Test results are presented over a wide range of operating speed, load angle and winding currents. These results indicate that the motor is a promising contender for urban transit propulsion.     

A DYNAMIC INDUCTION MOTOR MODEL INCLUDING SPACE HARMONICS

ABSTRACT

An induction motor model is presented which can be used to compute dynamic characteristics and which includes both asynchronous and synchronous parasitic torque effects owing to space harmonics. A new transformation is given which eases computation and enables the stability of the synchronous parasitic torque to be determined. The model is applied to the computation of the direct on line starting characteristic for a four pole, three phase cage machine with 36 stator slots and 28 rotor slots.     

CHARACTERISTICS OF A VARIABLE SPEED SYNCHRONOUS MOTOR

ABSTRACT

Theoretical analysis of the steady state and transient characteristics of a variable speed synchronous motor is presented for two types of control namely voltage control and current control while the supply frequency to the armature is controlled by the instantaneous rotor speed. A laboratory experimental scheme using cycloconverters is described which is used to verify the torque-speed characteristics of the motor with voltage control.     

Computer-Aided Design Of A Permanent Magnet Motor

ABSTRACT

Although neodymium-iron-boron (Nd-Fe-B) magnets have high-energy product with suitable magnetic and physical properties for applications in electrical machines, the design of permanent magnet (PM) motors is a complicated problem due to their complex geometries and PM material characteristics. This paper initially compares various PM motor geometries and describes their PM material outlay, armature reaction and mechanical integrity. By the employment of appropriately located air slots to reduce the armature reaction in conjunction with flux enhancement arrangement without detracting from its mechanical integrity, a new rotor geometry for a high-field high-speed PM synchronous motor is proposed. Computer-aided electromagnetic calculation and graphical evaluation are employed for the design and optimization of the proposed PM motor. An idea of ‘computer job delegation’ is proposed and implemented within the computer system to provide full utilization of each computer's capabilities as well as parallel operation of the design and optimization process. The proposed rotor geometry and design philosophy have been implemented to design a 3.2 kW 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.     

TRANSIENT PERFORMANCE OF A SYNCHRONOUS DRIVE FOLLOWING A SHORT STATOR CURRENT INTERRUPTION

ABSTRACT

The object of the study is torque and current stress after automatic reswitching of a salient-pole synchronous motor. The three parts of the simulated transient process are: phase-by-phase switching off, operation of the loaded motor isolated from the net and finally the performance after reswitching. The actual load torque as dependent on velocity is taken into account and the pulling into step is checked.     

Microprocessor Controlled Converter-Fed Synchronous Motor Using Subtransient Flux Model

Abstract

A digital control system has been investigated for converter-fed synchronous motors particularly in high power applications. Improved system ruggedness is ensured using subtransient flux reference synchronization. A simplified model of the converter-fed synchronous motor is studied and the optimal torque performance is determined. The proposed microprocessor-based control system is discussed in detail. Transient behaviour of the system is tested experimentally.     

FIELD WINDING DRAG AND NORMAL FORCES OF LINEAR SYNCHRONOUS HOMOPOLAR MOTORS

ABSTRACT

Drag and normal forces caused by the homopolar field winding in a linear synchronous homopolar motor (LSHM), having a segmented secondary of solid iron, are calculated. The analysis is based on the electromagnetic field theory. Numerical results are computed and some experimental results are also given. It is concluded that solid iron segmented secondary is suitable for high speeds (100 to 120 m/s).     

A NEW STATISTICAL DISTRIBUTION FUNCTION SENSITIVE TO RENEWABLE ENERGY SYSTEMS

ABSTRACT

Although design of the variable reluctance (switched reluctance( type of synchronous machine has experienced intense activity in recent years, relatively little effort has been expended on improving the torque capability of the synchronous reluctance type of motor drive. Based on the analysis presented in this paper, it appears that substantial improvements can be made in the design of such motor drives resulting in performance characteristics which match or, indeed, perhaps even exceed that of the induction machine.