Induction Permanent Magnet Research Articles

Computational Electromagnetics and the Search for Quiet Motors

The paper reviews the progress in understanding and modeling the noise and vibration and the stray fields produced by electric machines. In machines that are already quiet, numerical methods are necessary to find the smaller sources of vibrations or emitted electrical signals. Several examples are given for permanent magnet machines and induction motors.

Analysis of Inherent Magnetic Position Sensors in Symmetric AC Machines for Zero or Low Speed Sensorless Drives

This paper presents an analysis of inherent position sensors in ac machines. In ac machine drives, the attachment of a mechanical transducer or a structural modification is necessary for zero or low speed operation where the back electromotive force (EMF) is zero or low. However, designs for introducing a measurable saliency in the spatial impedances of structurally symmetrical ac machines without any periodic modulation will make it possible to build sensorless drives at zero or low speed. Thin bridges in the core slots of a stator or rotor take the role of inherent magnetic sensors in ac machines. In structurally symmetric ac machines, such as a surface mounted permanent magnet synchronous machine (SMPMM) or induction machine (IM), the saliency in the spatial impedances is built by the spatial saturation on the leakage flux paths. This can be explained by a machine model that considers the spatial saturation, analyzed by the finite element method, and verified experimentally on test machines. Employing this phenomenon in the design or selection of symmetric ac machines will enable zero- or low-speed operation in sensorless drives.

Line-Starting Three- and Single-Phase Interior Permanent Magnet Synchronous Motors—Direct Comparison to Induction Motors

The performance comparison of three- and single-phase line-start interior permanent magnet synchronous motors (LSIPMSMs) and induction motors (IMs) with equal squirrel-cage design and symmetric four-pole stator windings is presented. The finite element method was employed in analysis of steady-state synchronous performance of LSIPMSMs. A magnetically linear lumped parameter model was employed in analysis of line-starting performance of LSIPMSMs, where the electrical and also the mechanical subsystems were considered. The procedure which was used for the LSIPMSM design was validated by comparison of calculation and measurement results. The performance of three- and single-phase LSIPMSMs and IMs with equal squirrel-cage design was directly compared and evaluated, thus emphasizing impacts of the permanent magnet breaking torque and reluctance breaking torque on the LSIPMSM performance in the asynchronous operation region.

Effects of the Built-in Permanent Magnet Rotor on the Equivalent Circuit Parameters of a Permanent Magnet Induction Generator

The permanent magnet induction generator (PMIG) is a new type of induction generator (IG) that has a permanent magnet (PM) rotor inside a squirrel cage rotor. The squirrel cage rotor is linked to the shaft, and the built-in PM rotor is free to rotate against the shaft. One of the notable features of the PMIG is that the power density is higher compared to a conventional IG. In this paper, the effects of the built-in PM rotor on the equivalent circuit parameters are investigated to clarify the reason for the increased power density.

電圧不平衡下におけるPM誘導発電機の動作解析

This paper presents electrical and magnetic characteristics of a permanent-magnet induction generator (PMIG) under unbalanced grid voltages. The method of symmetrical components and two-dimensional finite element analysis (2D-FEA) are used to calculate these characteristics and the results are confirmed through experiments. Even if the voltage of power grids is unbalanced, the PMIG can operate at high efficiency over a wide range of slip and the built-in permanent-magnet (PM) rotor is little affected by the negative-sequence rotating field.

単相系統に接続したPM誘導発電機の性能解析

In this paper, the single-phase operation of a permanent-magnet induction generator (PMIG) is analyzed theoretically and experimentally and is compared to that of a conventional induction generator (IG) of the same size to evaluate its usefulness. Phase balancing is achieved by connecting a phase converter across their stator windings. Based on the method of symmetrical components, the steady-state performance of both the PMIG and the IG is theoretically predicted, and the results are verified through experiments. The PMIG exhibits a higher performance, in terms of output power, power factor, and efficiency, than the conventional IG.

A Technique for the Steady-State Analysis of a Grid-Connected Permanent-Magnet Induction Generator

This paper presents a technique by which the steady-state performance of a grid-connected permanent-magnet induction generator (PMIG) can be predicted more accurately. By applying the topological principle of duality, an equivalent circuit of the PMIG is derived that takes into consideration the core loss as well as the permanent-magnet (PM) excitation. The nonlinear parameters in the equivalent circuit are modeled using curve-fitting methods. Experimental results performed on a 2.2-kW prototype PMIG demonstrate the accuracy of the proposed technique.

Some Tricks for Modeling Rotating Electrical Machines Using Finite Elements

Despite worldwide efforts and many recent advances, electrical machine modeling using finite elements can be computationally very expensive, especially if three-dimensional models are required. This contribution is concerned with speeding up the process. Some examples of line start permanent magnet machines and induction motors are provided.

PM誘導発電機の磁界解析

The permanent-magnet induction generator (PMIG) is a new type of induction machine that has a permanent-magnet rotor inside a squirrel-cage rotor. In this paper, a new technique for the magnetic field analysis of the PMIG is proposed. The proposed technique is based on the PMIG's equivalent circuit and the two-dimensional finite-element analysis (2D-FEA). To execute the 2D-FEA, the phasors of primary and secondary currents are calculated from the equivalent circuit, and the input data for the 2D-FEA is found by converting these phasors into the space vectors. As a result, the internal magnetic fields of the PMIG can be easily analyzed without complicated calculations.

Nonlinear modeling of a permanent‐magnet induction machine

AbstractThis paper presents the nonlinear modeling of a permanent‐magnet induction machine (PMIM). The PMIM has a permanent‐magnet (PM) rotor that is free to rotate inside a squirrel‐cage rotor. The internal self‐excitation from this PM rotor allows the PMIM to operate at a higher power factor. Utilizing a duality between magnetic and electric circuits, an electrical equivalent circuit that can accurately include the nonlinearity of the excitation circuit is derived. Based on this equivalent circuit, a measuring method of circuit parameters and a calculation method of the steady‐state performance are explained. In addition, the generating characteristics of the PMIM in the grid‐connected mode are theoretically calculated to verify the validity of the derived equivalent circuit, and the results are confirmed through experiments. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 58–67, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10189

Performance Evaluation of a Permanent-Magnet Induction Generator

A permanent-magnet induction generator (PMIG) is a special induction machine self-excited from the inside of the squirrel-cage rotor by a permanent-magnet rotor (PM rotor). In order to evaluate the practical value of the PMIG, its steady-state performance is analyzed theoretically and experimentally. As a result, it was found that the PMIG exhibits good power factor and efficiency compared to a general-purpose induction generator (GPIG) of the same size.

Performance Prediction of a Stand-Alone Permanent-Magnet Induction Generator

A permanent-magnet induction generator (PMIG) is a special induction machine self-excited from the inside of the squirrel-cage rotor by a permanent-magnet (PM) rotor. The PMIG can be made to operate as a stand-alone generator when the squirrel-cage rotor is driven by an external prime mover. Moreover, if the capacitors are connected across the stator terminals, adjusting their values can control the output voltage. This paper presents a method for predicting the steady-state performance of such a stand-alone PMIG theoretically. By introducing the per-unit system, a nonlinear equivalent circuit, which can include the variation of the circuit parameters, is derived. Based on this equivalent circuit, the steady-state performance is theoretically calculated, and its validity is confirmed through experiments.

Nonlinear Modeling of a Permanent-Magnet Induction Machine

This paper presents the nonlinear modeling of a permanent-magnet induction machine (PMIM). The PMIM has a permanent-magnet (PM) rotor that is free to rotate inside a squirrel-cage rotor. The internal self-excitation from this PM rotor allows the PMIM to operate at a higher power factor. Utilizing a duality between magnetic and electric circuits, an electrical equivalent circuit that can accurately include the nonlinearity of the excitation circuit is derived. Based on this equivalent circuit, a measuring method of circuit parameters and a calculation method of the steady-state performance are explained. In addition, the generating characteristics of the PMIM in the grid-connected mode are theoretically calculated to verify the validity of the derived equivalent circuit, and the results are confirmed through experiments.

98/02239 Case study of the conversion of tangential- and wall-fired units to low-NOx combustion: Impact on fly ash quality

The paper presents the bacterial foraging optimization algorithm (BFOA) and particle swarm optimization (PSO) algorithm based robust controllers for voltage deviations due to the variation of reactive power in an isolated wind-diesel hybrid power system. The isolated wind-diesel system consists of wind energy conversion system (WECS) utilizing a permanent magnet induction generator (PMIG). Further, a synchronous generator (SG) is used with the diesel engine set for power generation. The mismatch between generated and consumed reactive power in the system causes voltage fluctuations, which will occur at generator terminals. These oscillations further causes reduction in the stability and quality of the power supply. The static synchronous compensator (STATCOM) and an automatic voltage regulator (AVR) are used to suppress voltage fluctuations in an isolated wind-diesel hybrid power system. The STATCOM is used as a reactive power compensator and the AVR is used to keep the terminal voltage constant for the synchronous generator. Both STATCOM and AVR are having proportional and integral (PI) controllers with single input. In modeling for the system, a normalized co-prime factorization is applied to show the possible unstructured uncertainties in the power system such as variation of system parameters and generating and loading conditions. The performance and robust stability conditions of the control system are formulated as the optimization problem, which is based on the Hα loop shaping. BFOA and PSO algorithms are implemented to solve this optimization problem and to achieve PI control parameters of STATCOM and AVR simultaneously. In order to show the efficiency of the proposed controllers, the performance of the proposed controllers is compared with the performance of the conventional controller and genetic algorithm (GA) based PI controllers for the same wind-diesel system. The dynamic responses of the system for four different small-disturbance case studies has been carried out in MATLAB environment.

Levitation and torque control of internal permanent magnet type bearingless motor

A general solution for levitation control applicable to permanent magnet (PM) synchronous and induction type rotating motors is presented. Levitation force is generated by the superposition of P+2 or P-2 pole magnetic flux with the usual motoring magnetic flux (pole number P). PM synchronous motors have the advantage that the control of rotation and levitation are independent, however, the levitation force is weak. Conversely, induction motors produce a strong levitation force, but their efficiency is poor and the control of rotation and levitation are coupled. This paper introduces an internal permanent magnet (IPM) type bearingless motor which has the merits of strong levitation force and relatively easy control properties. A simple experimental apparatus is made to confirm the properties of the proposed motor. The results obtained are discussed in detail.

Improvement of servomotors control laws with the help of finite element method

The present work is dedicated to the use of electromagnetic modelling in the control of electrical machines devoted to variable speed applications. Permanent magnet synchronous machines and induction machines are considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A neural network approach to real-time condition monitoring of induction motors

A neural network-based incipient fault detector for small and medium-size induction motors is developed. The detector avoids the problems associated with traditional incipient fault detection schemes by employing more readily available information such as rotor speed and stator current. The neural network design is evaluated in real time in the laboratory on a 3/4 hp permanent magnet induction motor. The results of this evaluation indicate that the neural-network-based incipient fault detector provides a satisfactory level of accuracy, greater than 95%, which is suitable for real-world applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Nonlinear analysis of a permanent magnet synchronous machine with nonsinusoidal stator winding currents

Permanent magnet synchronous machines and induction motors are often required to operate on-line starting or inverter-fed systems, which results in nonsinusoidal stator currents. These, in turn, give rise to undesirable harmonics and power losses which degrade motor performance. In this paper a time-domain analysis is presented for evaluating the magnetic field distribution in the two-dimensional cross section of the machine under load conditions. The analysis is applied to a permanent magnet synchronous machine under locked rotor conditions. Although for purposes of this analysis, the iron permeability has been assumed a constant, the method can be easily extended to include iron saturation.