Current Induction Motor Research Articles

Edge effect and independently supplied slot currents in tubular linear induction motor.

Edge effect and independently supplied slot currents in tubular linear induction motor.

Deadbeat control of induction motor current using state observer with adaptive poles selection.

For a high power induction motor drive, the switching frequency of inverter can not become higher than several kHz, and such switching, frequency produces a large current ripple, which in turn, produces torque ripple. To minimize the current ripple, a new method based on deadbeat control theory for current regulation is proposed. The PWM pattern is determined at every sampling instant based on stator currents measurements, motor speed, current references and rotor flux vector, which is predicted by a full-order observer with adaptive poles selection, so that the stator currents are controlled to be exactly equal to the reference currents at every sampling instant.The proposed method consists of two parts: (1) derivation of a deadbeat control; (2) construction of a full-order observer which predicts the rotor flux and the stator currents in the next sampling instant. This paper describes a theoretical analysis and computer simulations under various system conditions.

Performance analysis and evaluations of sinusoidal current instantaneous tracking-based three-phase inverter-fed induction motor load.

Performance analysis and evaluations of sinusoidal current instantaneous tracking-based three-phase inverter-fed induction motor load.

The causes and consequences of phase unbalance in single-sided linear induction motors

Unbalance in the phase currents of a single-sided linear induction motor (LIM) under balanced voltage operation is due to asymmetry of the primary windings and to the longitudinal end effect. Two methods of evaluating phase unbalance are presented. The first is analytical and is based on an equivalent circuit model. The second approach is numerical and uses the finite-element method. Computational results are validated by comparison with test results on a large-scale single-sided LIM. It is shown that phase unbalance produces a reduction in both thrust and normal forces, but this effect is likely to be significant only for high-speed LIMs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Control System Design of a Current Inverter Induction Motor Drive

An analytical design is presented of the control system of a slip-controlled current inverter induction motor drive. First of all, the drive dynamics are modeled in a control-oriented perspective. Afterwards, the transfer function between the rectifier output voltage and the inverter current is thoroughly analyzed and the results used to design the current controller. Two function generators are then synthetized and incorporated in the speed loop so as to obtain constant rotor flux operation and satisfactory torque dynamics. Lastly, the speed controller is designed for a fast and accurate response. All the parameters of the control system are given in terms of performance specifications and drive data. A computer implementation of the drive system is carried out and performance tests are shown.

Star-delta switching performance during the starting of an induction motor

During the starting of an induction motor currents are very high. Through the switching of the windings from a star- to a delta-configuration the currents are diminished. But there are high current and torque transients shortly after the switching moment. These transients are dependent on the type of the star-delta-connections and on the switching moment during the rup-up. This paper presents a through investigation of these dependencies and the resulting current and torque performance. Optimal switching moments will be discussed. The calculations are based on the presentation of the behaviour of the induction motor by space-phasors and is done by digital simulation on a computer. Great importance is put on a physical interpretation of the results.

Stabilization of Controlled Current Induction Motor Drive Systems via New Nonlinear State Observer

In this paper a new bilinear and nonlinear second-order state observer which is globally asymptotically stable is constructed to estimate the unmeasurable state variables. Then an unstable controlled current induction motor drive system which cannot be stabilized by a linear state observer is successfully stabilized by feeding the reconstructed state variables from the nonlinear observer to the frequency control channel. This scheme is easily implementable, resulting in an asymptotically stable overall closed-loop system. These results are numerically verified by simulation.

CALCULATION OF THE LOCKED ROTOR CURRENTS AND TORQUE IN INDUCTION MACHINES

ABSTRACT The analysis of certain end-winding vibration problems requires an accurate knowledge of the transient currents in an induction motor during the early part of the start-up period where the time rates of change of current are the highest. This paper details the derivation of expressions for the winding currents assuming that the machine remains at rest during the period of interest. Under these conditions, the currents are shown to contain three time dependent components, one of which is oscillatory, the remaining two being damped exponentials. The rates of decay of the exponential components are particularly important to some aspects of the vibration problem and they are shown to be dependent on the winding resistances and inductances and also upon the degree of coupling between stator and rotor.

A New Method for the Study of Inter-Bar Currents in Polyphase Squirrel-Cage Induction Motors

The paper presents an analysis of inter-bar currents and stray-load losses in non saturated polyphase squirrel-cage induction motors due to the harmonic currents in the cage and in the contact between cage and rotor laminations.

Conditions for Which the No-Load Current of an Induction Motor is Greater Than the Standstill Current

The conditions for which the ratio of no-load current to standstill current of an induction motor is greater than unity are discussed in algebraic and graphical terms. For a special case, where the Goodness Factor equals unity, the maximum ratio occurs when R1/ Xm equals the Golden ratio.

Modeling and Design of Controlled Current Induction Motor Drive Systems

A dynamic model for current-controlled induction motor drives is developed, and a transfer function approach to the transient response investigation is formulated by means of d-q variables in the synchronously rotating reference frame. A sample control strategy is discussed, and transfer functions for various combinations of input and output variables are presented. It is shown that both dynamic and static instabilities exist for open-loop operation, but a well-damped closed-loop response is possible if slip frequency and current magnitude control are imposed. A comparison between the analytical transfer function transient performance predictions, the transient respontse predicted by the hybrid computer simulation, and actual laboratory tests is made using frequency response techniques. Bode plots are used to correlate' the results between laboratory and analytical techniques. Hybrid computer and laboratory results are presented to show typical steady-state characteristics and waveforms.

State-Variable Steady-State Analysis of a Controlled Current Induction Motor Drive

The exact equations defining steady-state operation of a controlled current induction motor drive system are derived by solving the system state equations in the stationary reference frame. These equations, which assume ideal current filtering, eliminate the difficulties involved in taking derivatives of discontinuous currents by defining a pair of pseudocurrent variables. Effects of saturation are included by using the slope ratio method. Electromagnetic torque and current pulsations are computed for various load conditions, and experimental confirmation of the calculated results is made. Similarities and differences to voltage controlled characteristics are presented. It is shown that normal open-loop operation occurs on the unstable side of the torque-slip characteristic necessitating the use of feedback control for stable operation.

Design of controlled current AC drive systems using transfer function techniques

A dynamic linearized model and the associated equivalent circuit for a controlled current induction motor are presented. The controlled variables of interest are identified and open-loop transfer functions are tabulated. Openloop operation is shown to be inherently unstable for all operating conditions. Feedback control is used to stabilize the system while simultaneously yielding the desired steady state characteristics. Transfer function techniques are used to synthesize the necessary slip, current, and speed control loops for two closed loop speed control strategies. Ein dynamisch lineares Modell und der dazugehörige equivalente Stromkreis für den stromgesteuerten Asynchronmotor wird bespochen. Die massgebende, gesteuerte Wirkungsgrösse wird beschrieben und die Übergangsfunktionen für offenen Regelkreis tabuliert. Der Betrieb mit offenen Regelkreis ist naturgemäss labile Rückführungen werden verwndet, die nicht nur stabilisieren sondern auch den gewünschten Ruhestand ergeben. Übergangsfunktionen werden verwendet, die den benötigten Schlupf, Strom und Drehzahlsteuerung für einige geschlossene Drehzahlsteuerbereiche synthetisch aufbauen.

Sources of harmonic currents in slip-ring induction motors

Several features which could cause an unsaturated 3-phase induction motor to draw nonsinusoidal currents from a supply of negligible harmonic content are examined. An analysis is developed which provides a simple method for the prediction of the harmonic-current magnitudes and frequencies. A comparison of predicted and measured current harmonics is presented to substantiate the theory.

Model of Multiphase Induction Motor

The six-phase induction motor with two similar stator three phase windings, shifted by 30 degrees in space and three phase winding in rotor is considered. Differential equations of this motor are presented and transformed to dq synchronous reference frame. Dynamic equivalent circuits for each component are presented. Transformed equations are expressed in matrix form and are solved by MATLAB software using Dormand-Prince (ode45) method. Transient characteristics of torque, speed and current of six-phase induction motor are calculated and discussed. Ill. 6, bibl. 12, tabl. 1 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.111.5.369

Equivalent Circuits with Transformer Elements for Eddy Current Rotor Induction Motors Derived from Field Equations II-Drag Cup Rotor Motors

The characteristic problem in analysis of drag cup rotor motors by field theory is that field equations appear with different coefficients and co-ordinates in sleeve and web sections. By solving for both sections separately and synthesizing the complete field pattern, an equivalent circuit is derived in a manner similar to that for sleeve motors. Hence, performance characteristics can be computed readily. Examples of such calculations are given for both sleeve and drag cup rotor motors in Appendixes I through III, and test results are presented.

Equivalent Circuits with Transformer Elements for Eddy Current Rotor Induction Motors Derived from Field Equations I-Sleeve Rotor Motors

The characteristic problem in analysis of drag cup rotor motors by field theory is that field equations appear with different coefficients and co-ordinates in sleeve and web sections. By solving for both sections separately and synthesizing the complete field pattern, an equivalent circuit is derived in a manner similar to that for sleeve motors. Hence, performance characteristics can be computed readily. Examples of such calculations are given for both sleeve and drag cup rotor motors in Appendixes I through III, and test results are presented.

Saturistors and Low Starting Current Induction Motors

By locating a hard magnetic material, such as Alnico, in the leakage flux paths of the secondary circuits of an induction motor, a remarkably high locked-rotor torque per ampere can be obtained, without sacrifice of full-load speed. This paper presents test data for both wound-rotor and squirrel-cage motors, using this Saturistor principle. The motors so made are series hysteresis (induction) motors, with completely different characteristics from the familiar shunt-type hysteresis (synchronous) motor.

Saturistors and low starting current induction motors

By the use of a hard magnetic material, such as alnico, in the leakage-flux paths of the secondary circuits of an induction motor, a remarkably high locked-rotor torque per ampere can be obtained without the sacrifice of full-load speed. Test data are presented for both wound-rotor and squirrel-cage motors employing this “Saturistor” principle

Rotor-bar currents in squirrel-cage induction motors

Rotor-bar currents in squirrel-cage induction motors