Dynamic model of an integral-cycle controlled single-phaseinduction machine

A dynamic machine model of an integral-cycle-controlled single-phase induction motor is derived by properly choosing a stationary d-q reference frame. The approach highlights the mode transition which occurs in the integral-cycle operation. By utilizing the model it is revealed that two types of capacitor connection to the machine windings are equivalent, and that the integral-cycle controlled single-phase induction machine switches its operation between two distinct modes. A comparison of simulated to test results indicates that with the integral-cycle control, a complicated motor behavior may occur due to the irregular current waveform in its operation     

A complete lumped equivalent circuit of three-phase squirrel-cage induction motors using two-dimensional finite-elements technique

The paper presents the use of the finite element technique for determining the parameters of a three-phase squirrel-cage induction motor. The common parameters in addition to the core losses and ratio of number of turns are obtained from the finite-element field solutions. The magnetizing characteristic and core losses curve are used to determine the flux distribution within the motor structure. The linear time harmonic vector potential field solution is used for the inductances computation. The accuracy of the finite-element application is verified using the available precise results.     

Temperature rise of an induction motor during plugging

The problem of three-dimensional transient heat flow in the stators of induction motors is solved using a finite-element formulation employing arch-shaped elements. The shape functions and exact solutions are derived algebraically for the utmost economy in computation. The temperature distribution has been determined considering convection from the surface and the two ends. The temperature distribution has also been determined by specifying the temperature of the surface and the ends. A simple cylinder is used as an example. The temperature at different locations in the stator of the induction motor has been computed during transients     

Use of a permeance model to predict force harmonic components and damper winding effects in salient-pole synchronous machines

This paper presents a combined finite-element and analytical modeling technique for the prediction of force-density harmonics in salient-pole synchronous machines. The model calculates the induced currents in the damper winding cage and includes their effect on force-density components in the solution. Use of a combined analytical and finite-element approach considerably reduces simulation times compared to full time-stepping finite-element solutions, while including the effects of design changes on air-gap force harmonics. Results of the model predictions are presented together with measured data from two different machines.     

Analysis of torque developed in axial flux, single-phase brushless DC motor with salient-pole stator

An analysis of the torque developed by a single-phase disc brushless permanent magnet motor with salient-pole stator is presented. The machine represents a new family of brushless disc motors with the starting torque issue appearing to be most challenging. To produce a starting torque, the permanent magnets on one of the rotor discs are distributed nonuniformly. However, this significantly distorts a shape of the cogging torque versus rotational angle characteristic which, in turn, affects a waveform of the overall torque. A three-dimensional (3-D) finite-element model is used for the purpose of determining of angular variations of the torque developed by the motor. To find how the torque varies with time, a model of the source-inverter-motor circuit is developed. A simulation study on an influence of the commutation angle on the electromagnetic torque is also a subject of this paper. The results obtained show that the motor performance can be improved by a proper selection of the current commutation angle to reach the maximum efficiency. The simulation results are in good agreement with measurements obtained from a prototype motor.     

A Field Reconstruction Technique for Efficient Modeling of the Fields and Forces Within Induction Machines

Traditional analysis and design of induction machines have been largely based upon lumped-parameter models. An alternative tool used for field-based evaluations of an induction machine is the finite-element method. Although useful, its computational complexity limits its use as a design tool. In this paper, a field reconstruction (FR) method for induction machine simulation is introduced. The FR method utilizes a small number of finite-element evaluations to establish basis functions of normal and tangential flux densities. The basis functions are then used to estimate the magnetic field under arbitrary stator excitation. Using such a tool, evaluation of fields and forces produced by a machine under alternative excitation strategies can be explored efficiently. Moreover, alternative field-based derivation of stator/rotor excitation control can be explored.      

Simulation Studies of the Transients of Squirrel-Cage Induction Motors

A new simulation approach is proposed in consideration of a saturation and a deep bar effect for the study of transients of three-phase squirrel-cage type induction motors. The mathematical model of an induction motor is expressed by the six differential equations of three-phase instantaneous voltage and current. The torque of an electric equation is related to the motion equations of motor and driven machine in the mathematical model. The values of reactance of stator and rotor are changed by the saturation of core caused by starting current. Also both the values of reactance and resistance of rotor bar are varied by the deep bar effect in the rotor core during starting. The calculation method of circuit constant that adds the influence of saturation and deep bar effect is proposed in this paper. The circuit constant of simulation model in consideration of saturation and the deep bar effect are decided by these computation methods in accordance with the conditions of rotation speed and current. If the large current flows, the leakage reactance of the stator and the rotor decreases by saturation. Moreover, the resistance of the rotor gradually decreases when the rotational speed rises from stop to synchronous speed, and the leakage reactance increases gradually. The calculated values were compared with the observed values of the examination machine of 1100 kW4P and an excellent agreement was obtained demonstrating the accuracy of the proposed simulation. Consequently, it is shown that the saturation and the deep bar effect are the essential factors to perform the accurate simulations of the induction motor. After checking the validity of the proposed approach, the simulation of the grounding faults was performed. In this study, all the simulation programs have been developed in the Matlab/Simulink environment.     

Numerical study of convective heat transfer of nanofluids in a circular tube two-phase model versus single-phase model

Laminar convective heat transfer of nanofluids in a circular tube under constant wall temperature condition is studied numerically using a CFD¹ approach. Single-phase and two-phase models have been used for prediction of temperature, flow field, and calculation of heat transfer coefficient. Effects of some important parameters such as nanoparticle sources, nanoparticle volume fraction and nanofluid Peclet number on heat transfer rate have been investigated. The results of CFD simulation based on two-phase model were used for comparison with single-phase model, theoretical models and experimental data. Results have shown that heat transfer coefficient clearly increases with an increase in particle concentration. Also the heat transfer enhancement increases with Peclet number. Two-phase model shows better agreement with experimental measurements. For Cu/Water nanofluid with 0.2% concentration, the average relative error between experimental data and CFD results based on single-phase model was 16% while for two-phase model was 8%. Based on the results of the simulation it was concluded that the two-phase approach gives better predictions for heat transfer rate compared to the single-phase model.     

Performance Study of a Doubly Fed Wind-Power Induction Generator Under Network Disturbances

Transient performance of a 1.7-MW wind-power doubly fed induction generator (DFIG) under network disturbances is studied using a coupled field-circuit simulator. The simulator consists of the finite-element method model of a DFIG coupled with the circuit model of the frequency converter, a transformer, and a simple model of the network. The simulation results show the transient behavior of the DFIG when a sudden voltage dip is introduced. The field-circuit simulator is experimentally validated by full-power measurement     

Comparison between single- and multiple-zone induction heating of largely curved mold surfaces

This study applied three-dimensional steady-state finite-element numerical simulations of electromagnetic fields and temperature distributions to evaluate the effects of various coil geometries, regional depositions, and magnetic shielding materials on the induction heating of a curved mold plate surface used for fabricating automotive spoilers. Conventionally, the induction heating of large mold surfaces by using a set of long inductive coils entails employing a costly, high-power induction heating device. This study proposes a multizone induction heating approach that entails dividing a target surface into several zones and then applying numerous sets of short inductive coils that require only low-power induction heating devices to the individual regional zones for heating. In this approach, the coil design is relatively simple for efficiently heating these small-area zones. The simulation results are described as follows: (1) the geometry of the inductive coils with respect to the processed workpiece demonstrated a considerable effect on the electromagnetic field distribution and the heating efficiency of the system. (2) Magnetic shielding materials facilitated eliminating the proximity effect, which produces a nonuniform heating pattern along the workpiece wall. (3) Compared with single-zone induction heating, the multiple-zone induction heating of a largely curved mold surface enhanced the heating rate and uniformity performance.     

Three dimensional magnetic fields in extra high speed modifiedLundell alternators computed by a combined vector-scalar magneticpotential finite element method

A three-dimensional (3-D) finite-element (FE) approach was developed and implemented for computation of global magnetic fields in a 14.3 kVA modified Lundell alternator. The essence of the method is the combined use of magnetic vector and scalar potential formulations in 3-D FEs. This approach makes it practical, using state-of-the-art supercomputer resources, to globally analyze magnetic fields and operating performances of rotating machines which have 3-D magnetic flux patterns. The 3-D FE computed fields and machine inductances as well as various machine performance simulations of the 14.3-kVA machine are presented     

PSPICE simulation of single-phase induction motors

Dynamic analysis of a single-phase induction motor is studied using PSPICE software. The machine dynamics are presented by a set of nonlinear time-varying differential equations. The equations which define the motor operation are represented in an orthogonal system. The electric circuit presenting this set of equations is determined and solved by PSPICE software for simulation of the motor. The simulation results are compared with those obtained by EMTP and the experiment. Good agreements are observed for both cases     

Performance analysis of single-phase line-start permanent-magnet synchronous motor

Single-phase line-start permanent magnet (LSPM) synchronous motors have always been far less amenable to detailed computer-aided performance analysis compared with three-phase LSPM synchronous motors. The main reason is the lack of an accurate mathematical model of the motor characteristics arising from the unbalanced stator field and the rotor saliency. However, there is great potential for these types of motors to replace conventional single-phase induction motors in many domestic applications on account of their higher efficiencies when properly designed. In this paper, a new model that is applicable to both synchronous and asynchronous operation of the motor is proposed in which the parameters can be readily obtained by the two-dimensional (2-D) static finite-element method (FEM). It includes both the forward and backward rotating magnetic fields. It can be used to analyze the torque versus slip characteristics and predict the steady-state performances of the motor quickly with reasonable accuracy. The model has also been extended to simulate the transient start-up process and other dynamic performances. The models are suitable for the initial design and optimization of the motor geometry because of its low run-time overheads. Experimental results have verified the practicability of the models.     

A capacitor start three phase induction motor

A scheme for the fast starting of three-phase induction motors is proposed. This scheme is based on starting the motor from a single-phase power supply with the help of a phase balancer properly selected for achieving maximum starting torque. As the speed reaches a predetermined value, a simple centrifugal switch is used to reconnect the motor to the three-phase supply. The feasibility of the proposed scheme is proven through the development of a rigorous state-space mathematical model and its associated digital simulation, followed by experimental verification     

Grey Predictor reference model for assisting particle swarm optimization for wind turbine control

This paper proposes an approach of forming the average performance by Grey Modeling, and use an average performance as reference model for performing evolutionary computation with error type control performance index. The idea of the approach is to construct the reference model based on the performance of unknown systems when users apply evolutionary computation to fine-tune the control systems with error type performance index. We apply this approach to particle swarm optimization for searching the optimal gains of baseline PI controller of wind turbines operating at the certain set point in Region 3. In the numerical simulation part, the corresponding results demonstrate the effectiveness of Grey Modeling.     

A laboratory model for harmonic measurements in windpowergenerators

In this letter we present the principles of an integrated control and measurement system which is linked to a DC servo motor used to drive a single-phase induction machine. The role of the DC servo motor is to model the drive from the turbine of a wind energy conversion system (WECS). This drive is in turn physically connected to a single-phase induction machine that is in turn linked to an external single-phase supply and various loads applied. Measurements of the harmonic components from the system are obtained from a desktop computer with analog to digital interface cards running programs developed under LabVIEW software. The system demonstrates the greatest change in harmonic components just before onset of power generation and thereafter settles to a constant level. Work is planned to expand the system to include more nodes, three phase capabilities, and reactive power electronic control     

An analysis of single-phase self-excited induction generators:model development and steady-state calculations

The modeling and steady-state performance of single-phase induction generators based on the principles of harmonic balance is set forth in this paper. Magnetizing flux linkage saturation and flux dependent core loss resistances are included. Experimental results are provided to justify the analytical approach and steady-state calculations     

A Finite-Element Model for the Thermal Radiative Properties of Graded Index Fiber Coated with Thin Absorbing Film

A finite-element model in combination with the wave optical approach is developed based on the radiative transfer equation for graded index medium in cylindrical coordinate system to predict the total hemispherical thermal radiative properties of semitransparent graded index fiber coated with thin absorbing film. The film is made of a strong absorbing medium with thickness less than or on the order of the wavelength of peak magnitude of thermal radiation. Radiative absorptance of the fiber-film system is directly obtained by solving the radiation deposited in the system. Radiative transfer in the fiber is solved by a least squares finite-element method, while radiative transfer in the thin film is treated through wave optics, and the film is formulated as a special kind of semitransparent boundary condition for the fiber medium. The results obtained by the finite-element model for uniform index fiber are in good agreement with the results in the literature obtained through the ray tracing model. The effects of fiber refractive index distribution on predicted thermal radiative properties are investigated. For the fiber with or without film, the variation of refractive index distribution has a substantial influence on the effective emittance.     

Identification of induction motor equivalent circuit parametersusing the single-phase test

In this paper, a new method of identification of the induction motor equivalent circuit parameters is introduced and discussed. The proposed method uses single-phase test results as a base test for calculating the equivalent circuit parameters of the induction motor. The single-phase test is performed using a variable frequency power supply (inverter). The test was conducted at various frequencies while the voltage, current and power factor were measured. Thereafter, the motor parameters are calculated. The precision of calculation of the motor parameters is sensitive to the accuracy of measurements which can be improved by the use of high performance microprocessors     

Non-adiabatic capillary tube flow: a homogeneous model and process description

This paper presents a homogeneous model of refrigerant flow through capillary tube–suction line heat exchangers, which are widely used in small vapour compression refrigeration systems. The homogeneous model is based on fundamental conservation equations of mass, momentum and energy. These equations are solved simultaneously through iterative process. Churchill’s correlation [3] is used to calculate single-phase friction factors and Lin et al. [6] correlation for two-phase friction factors. The single-phase heat transfer coefficient is calculated by Gnielinski’s equation [5] while two-phase flow heat transfer coefficient is assumed to be infinite. The model is validated with previous experimental and analytical results. The present model can be used in either design calculation (calculate the capillary tube length for given refrigerant mass flow rate) or simulation calculation (calculate the refrigerant mass flow rate for given capillary tube length). The simulation model is used to understand the refrigerant flow behaviour inside the non-adiabatic capillary tubes.