Double-cage Induction Machine Research Articles

Indirect Vector Control of Multi Cage Induction Motor

This paper presents a methodology for indirect vector control of a double cage induction motor. Vector control or field oriented control offers more precise control of high performance drives where oscillations in air gap flux linkages are intolerable. The mathematical model of a double cage induction machine is proposed. The developed model is studied with constant V/f control taking the boost voltage into account and indirect vector control. A comparison is made between the two control methods. Finally Simulation results have shown better results with indirect vector control compared to constant V/f control. General Terms Double-cage induction machine model, Indirect vector control, constant V/f control.

Numerical impulse response test to identify parametric models for closed-slot deep-bar induction motors

An impulse response test for estimating the electrical parameters of a deep-bar induction motor is studied. The impulse response test is performed within the two-dimensional finite-element analysis (FEA). The impulse excitation is applied to the stator voltage. Since the test is suitable for modelling the perturbations about a certain operation point, a small-signal model for the double-cage induction machine is derived. The skin effect is taken into account by using two parallel rotor branches. In addition to the small-signal parameters, the steady-state parameters are also estimated using the time-harmonic FEA. The impulse response test is based on the assumption of linear behaviour about an operation point. Thus, the effects of nonlinearity are studied by several methods.

Abc/qd, qd/abc Model of a Double-Cage Induction Machine and Determination of Parameters Using the Genetic Algorithm

In this paper the mathematical models of a double-cage induction machine (DCIM) in qd/abc and abc/qd reference frames are presented. A detailed study of the rotor structure of this machine provides the mutual inductance between the top and bottom slots in the rotor. When the transient model of this machine is obtained from the universal machine model (synchronous machine model with damper windings), the effect of this mutual inductance does not appear in the qd/qd model of the induction machine. The abc/qd and qd/abc models obtained here are compared with the standard qd/qd model of the DCIM. The experimental work is carried out on a 5.5 kW machine to investigate the validity of parameter determination using the genetic algorithm.

Analysis of the induction machine parameter identification

This paper analyzes the numerical identifiability of the electrical parameters of induction machines. Formulations of the single and double-cage induction machine, with and without core-losses in both models, are developed. The impossibility of identifying all the parameters of these models when only external measurements (voltage, current, speed and torque) are used is shown. One proposed solution is the formulation of machine equations by using the minimum number of parameters (which are identifiable parameters). As an application example, the parameters of a double-cage induction machine are identified using steady-state measurements corresponding to different angular speeds.

Analysis of the Induction Machine Parameter Identification

This paper analyzes the numerical identifiability of the electrical parameters of induction machines. Formulations of the single-and double-cage induction machine, with and without core-losses in both models, are developed. It is shown the impossibility to identify all the parameters of these models when only external measurements (voltage, current, speed, and torque) are used. One proposed solution is the formulation of machine equations by using the minimum number of parameters (which are identifiable parameters). As an application example, the parameters of a double-cage induction machine are identified using steady-state measurements corresponding to different angular speeds.

Modeling and Experimental Study of 3-Phase Short-Circuits of a Double-Cage Induction Machine

Three-phase short-circuits of the induction machine yields to high levels of stress in an induction traction drive. To study these operations, the authors propose to model the machine by a multiple cage equivalent circuit. This enables us to take into account the deep bar effect with accuracy. The identification of the equivalent circuit and its validation are carried out experimentally for a 30-kW double-cage induction motor.

An introduction to electric machine modeling by systems of noninteger order. Application to double-cage induction machine

The flowing of induced currents in electric machines, especially in the deep-bars of induction machine cages and the dampers of synchronous machines, implies an increase in the order of the equivalent circuits used to model their frequency response. But, physical meanings of the circuit parameters are often lost. Thus, the authors propose to go back over the modeling of skin effect in order to define noninteger order equivalent circuits which would be linked with the consequences of induced currents on the frequency response. In this paper, the proposed equivalent circuit is based on half-order systems. It is used to represent the frequency response of a 30 kW 4 pole double-cage induction machine and its results are compared with measurements.

Pseudorotor-flux-oriented control of an induction machine for deep-bar-effect compensation

In an induction machine with deep rotor bars, the rotor parameters change due to skin effect and saturation, and the skin effect is often modeled as a ladder network. For the high-performance drive of an induction machine with deep bars, many sophisticated control strategies and machine models have been discussed. As a control strategy, a complicated airgap flux-oriented control scheme is mostly adopted, because it is not possible to define a unique rotor flux in the deep bar model. However, a unique pseudorotor flux can be defined, and it is straightforward to achieve independent control of pseudorotor flux and torque. This control scheme can be applied to any nth multiple ladder network. In this paper, it is shown how a deep-bar effect of an induction machine can be negligible by performing the proper field-oriented control. By using the concept of pseudorotor flux, the conventional rotor-flux-oriented control using equivalent rotor parameters is effective for deep-bar and/or double-cage machines. The actual insulated gate bipolar transistor (IGBT) inverter systems with a high-precision torque transducer are implemented and thoroughly tested on a 250 hp induction machine and a 5.5 kW double-cage induction machine to confirm their validity.

Modelling of magnetic saturation in smooth air-gap synchronous machines

Main flux saturation in d-q axis representation of synchronous machines is at present modelled by selecting either all the winding currents or all the winding flux linkages as state-space variables. However, these two available models are just a tiny portion of the complete set of models that can be obtained by selecting other combinations of state-space variables. This paper presents a general procedure for main flux saturation modelling in smooth air-gap synchronous machines, that is applicable for most selections of state-space variables. The method relies on the concept of 'generalised flux' and 'generalised inductance', that has been successfully applied in modelling of saturated single-cage and double-cage induction machines. The concept is extended to saturation modelling in smooth air-gap synchronous machines. A number of models, that result from the application of the method for different selections of state-space variables, are presented in detail.

Capacitor braking of double-cage induction motors

Capacitor braking relies on the self-excitation process and represents a well-established technique of braking of single-cage induction machines. However, there appear to be no papers on the capacitor braking of double-cage induction motors. Since the self-excitation process constitutes the basis of capacitor braking, a correct representation must include the effects of main flux saturation in the induction machine model used. The paper first summarises the mathematical model of a saturated double-cage induction machine and then presents experimental results together with results of a comprehensive simulation study. Both symmetrical three-phase and asymmetrical single-phase capacitor braking techniques are considered. The results are shown for two different double-cage induction machines. The experimental and simulation results are found to be in good agreement.

SIMULATION OF SATURATED DOUBLE-CAGE INDUCTION MACHINES

ABSTRACT By using space-vector theory the effects of saturation of the main and leakage flux paths are incorporated into various transient models of a double-cage induction machine. The first two models utilize the currents as the state-variables and the equations are expressed in the stationary and synchronously rotating reference frames respectively. These models also incorporate the effects of cross-magnetization. The new terms in the impedance matrices are caused by main and leakage flux saturation and depend on both the position and the modulus of the appropriate space vector of currents. The third model which uses the flux linkages as the state-variables is simpler than the first two, but it conceals the effects of cross-magnetization and also some other effects due to saturation. The fourth model also uses the flux linkages as state-variables, but the equations are formulated in a special reference frame and it is suitable for application in a drive employing magnetizing-flux-oriented control. Results of digital computer simulations are also presented

General method of magnetising flux saturation modelling in d–q axis models of double-cage induction machines

Two models of induction machines with two rotor windings, that include magnetising flux saturation, are available at present: the first one is the current state-space model, where state-space variables are selected as d-q axis components of stator and both rotor currents; while in the second model state-space variables are d-q axis components of stator and both rotor flux linkages. The paper presents a general procedure for inclusion of magnetising flux saturation in a d-q axis model of induction machines with two rotor windings. Using the procedure, it becomes possible to derive a model of a saturated induction machine with two rotor windings for any selected set of state-space variables. The approach to magnetising flux saturation modelling relies on the concept of 'generalised flux space vector', which has recently been introduced for single-cage induction machines. Several characteristic models of a saturated induction machine, derived by applying the concept of the generalised flux space vector, are presented in detail. In order to verify the models, an extensive simulation study of the double-cage induction generator self-excitation process is performed, accompanied by the corresponding experimental investigation. The main results of the study are included. Finally, advantages of some of the novel models over the existing ones and possible applications are addressed.

Main flux saturation modelling in double-cage and deep-bar induction machines

The available models of saturated double-cage and deep-bar induction machines are the current state-space model and the flux state-space model, where state-space variables are selected either as stator current and currents of both rotor cages, or stator flux linkage and flux linkages of both rotor cages. This paper presents a number of models of saturated double-cage (deep-bar) induction machines where alternative sets of state-spate variables are selected. The method of main flux saturation modelling relies on recently introduced concept of 'generalised flux space vector', which has originally been developed for modelling of saturated single-cage induction machines. The procedure and the novel models are verified by experimental study and simulation of self-excitation process in a double-cage induction generator.

Modelling of deep-bar and double-cage self-excited induction generators for wind-electricity generation studies

The paper presents the derivation of a current state-space model of saturated deep-bar and double-cage induction machines. The approach adopted in the paper closely parallels that utilized in the derivation of the current state-space model of a saturated single-cage induction machine. The developed model is then adapted to the terminal conditions met in the self-excitation of induction generators. Simulation of voltage and current build-up during self-excitation is performed. Simulation results are confirmed by experimental investigation, thus providing verification of the derived saturated double-cage induction machine model. It is believed that the model could be very useful in transient studies concerning unconventional energy sources, especially wind-electricity generation.

Field-oriented controllers with rotor deep bar compensation circuits (induction machines)

A rotor deep bar effect compensation circuit for field-oriented controllers is derived from the transient equations of a double-cage induction machine. Torque and flux are decoupled with respect to the airgap flux. Accurate tuning of the field-oriented controller is possible both for steady-state and high-frequency conditions in the rotor. Consequently, an extended static stability region and improved torque dynamics are obtained with the deep bar effect compensated induction motor drive. >

Decomposed, Reduced Order Model for Double-Cage Induction Machines

A method is presented and validated for increasing the computational efficiency in simulating double-cage induction machines where stator transients are to be included. Iterative decomposition is used to separate the flux-linkage equations into decoupled fast and slow subsystems, after which the model order of the fast subsystem is reduced by neglecting the heavily damped fast transients caused by the starting cage. The two decoupled subsystems along with the equation for the very slowly changing slip constitute a three time-scale model for the machine which resulted in more than doubling computational speed.

Decomposed, Reduced Order Model of Double-Cage Induction Machines

Decomposed, Reduced Order Model of Double-Cage Induction Machines

Decoupled boundary layer model of induction machines

A partially decomposed variable-order model of the double-cage induction machine is presented and validated. The model exhibits improved computational efficiency in simulating full machine behaviour including stator transients. A state variable transformation is used to separate the electrical steady-state from the transient part of flux linkage response. The transient flux-linkage response is next decomposed into fast and slow sub-systems which constitute the boundary layers of the overall model. The fast subsystem is then reduced by neglecting the heavily damped fast transients caused by the starting cage. Each of the two decoupled boundary layer equations may be computed using different time steps and even ignored during periods when the corresponding mode is not excited, thereby effectively reducing model order and greatly decreasing computational requirements while retaining simulation accuracy.