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A survey of small-scale electricity generation technologies is presented and the benefits derived from small-scale electricity generation are assessed. Small-scale generation is also known as the distributed generation, embedded generation or decentralized generation.

This paper discusses the sensitivity of adjustable speed drives (ASDs) to voltage sags and short interruptions on the basis of extensive test results. Existing standards and previously published work are critically reviewed, and a description of test procedures needed for appropriate assessment of ASD sensitivity is presented. The following tests were performed: sensitivity to rectangular three-phase, two-phase, and single-phase voltage sags with ideal and nonideal supply characteristics, as well as sensitivity to nonrectangular-balanced three-phase voltage sags similar to those caused by the starting of large motors. The results show that although the behavior of this equipment has a rather complex pattern, a simple representation of ASD sensitivity to various types of voltage sags and short interruption can be established. Index Terms--Nonideal power supply characteristics, power quality, rectangular and nonrectangular three-phase, two-phase, and single-phase voltage sags and short interruptions, voltage-tolerance curve.

The paper presents the use of the finite element method for determining the parameters of a two-axis model of a three-phase cage induction machine. The model parameters are obtained from. the finite element field solutions. The saturation of the motor is taken into account in calculation of the flux distribution by using a static non-linear vector potential solution. The linear time harmonic vector potential field solution is used for the inductances determination. All the inductances are determined as functions of the magnetizing current. Rotor skew is also taken into account. The accuracy of the described identification procedure is verified through laboratory measurements of the parameters. Keywords - Induction Motors, Two-axis Models, Parameter Calculation, Finite Elements

The paper describes the steady state analysis of squirrel cage induction motors using a two-dimensional finite element solution. Saturation is included using an iterative process combining both static and time-harmonic solutions. The motor end-effects are calculated using 2d and 3d finite elements including a lumped parameter approach during the solution of the time-harmonic problem. Both motors types, with closed and open rotor slots are analysed. Different operating points for load, no-load and locked rotor situations are analysed and compared. The influence of the different end-effect parameters is analysed by including or neglecting them in the calculations. Good agreement with measurements are found for all operating conditions. The calculations are performed using a commercial FEA package.

This paper presents a computer-based method for finding the optimum geometry of very small electrostatic motors based on the variable capacitance principle. Not only is the geometry taken into account, but different excitation schemes are studied, in order to find the maximum average output torque and/or the minimum vibration component in the output torque. Different combinations of stator and rotor poles are treated. The most important part of this optimization is automation of the procedure. For the actual calculation of the electrostatic field distribution, the finite-element method is used. The mesh generation for the machine as a function of the rotor position and the design parameters is automated. The extraction of the torque and capacitance values is done in batch procedure, constructed around a commercial finite-element CAD package. This automation makes the system into an optimization tool of an otherwise very tedious technique.

The distinction will be made between the vibrations produced by the fundamental current supplying the machine, and the much smaller higher harmonic currents, with frequencies ranging into the kilocycles range. The further discussion concentrates on the small harmonic currents. An appropriate mathematical modelling technique will be presented. A mechanical model is selected based on modal analysis techniques. A method is developed for finding the driving force for each mode shape. This is illustrated with measurements on a permanent magnet machine.

This paper considers the problem of magnetic flux variation in the rotors of vent-cooled, two pole induction machines. The solution to this problem is important, not only to reduce stray losses in such machines, but also to identify the location of hot spots to estimate their effects on the design. A second objective behind the research was to reduce the magnitudes and, as a result, the variations in shaft magnetic fluxes. Reducing shaft fluxes will result in reduced shaft failures due to fatigue that is exacerbated by repeated heating and cooling. A procedure is suggested for examining the effects of the placement of the vent holes on flux variations, especially in the shaft. Once the effects of flux variations are known, the heating effect can be deduced.

Presents the Belgian viewpoint on the educational curriculum for engineering at the university level. Discusses existing program content and compares it to European professional standards. Gives ideas about improvements that consider technical developments and professional aims. (CW)

Describes the use of computer-aided design (CAD) techniques in teaching the design of electrical motors. Approaches described include three technical viewpoints, such as electromagnetics, thermal, and mechanical aspects. Provides three diagrams, a table, and conclusions. (YP)

Disc-type motors with sintered Nd-Fe-B magnets benefit from the high remanence and near-ideal loop shape of the hardmagnetic material. Consequent advantages include a high torque for a given motor size and improved efficiency. Special airgap windings manufactured as multilayer etched windings contribute to flat package motors and to low torque harmonics. Different back iron designs were examined. For the operation of the brushless dc motor instead the classical hall sensors small magnetoresistive sensors can be used effectively for rotor position sensing.

The paper describes a general design tool that can be used for small and extra small electric and magnetic devices. Such devices generate micro motions. Due to their dimensions and specially due to the short axial length compared to the radial dimensions a three dimensional analysis of the field is required. Complex geometries recommend a well tuned engineering tool to guarantee reliable results. Here, a standard three dimensional finite element approach is chosen to compute the electric and magnetic field quantities respectively. In combination with a user-friendly computer interface, controlling the necessary finite element procedures, a powerful engineering tool with a general application range is obtained. For that reason it was possible to apply numerical optimization algorithms to realize a fully automated design tool. Various configurations are studied using the same software tools. The paper aims on the application of the finite element method (FEM). Keywords: electrostatic micro motor, sub-fractional horse power motor, finite element method, 3D field computation, design tools.

The paper describes a set of experiments and discusses their results for determining the efficiency of low voltage, three phase squirrel cage induction motors. The measured efficiency of an induction motor directly connected to the grid, strongly depends on the method used to evaluate the results and the standard according to which the measurements are performed. Different standards as IEEE 112 and IEC 32 are mentioned and their similarities and differences are discussed. The main discrepancies between the various standards is the way in which the values for the stray load losses are obtained at different load levels. A short description of the measurement setup is given and measurement results for motors of several manufacturers accounting for different standards are proposed. The results clearly demonstrate the necessity to handle the efficiency data given by the manufacturer with a lot of care. Keywords: induction motor, efficiency, standards, stray load losses

Electroplated micromagnetic components, such as planar and toroidal inductors and transformers with ferromagnetic cores are promising devices. The characteristics of the materials used in these micro-scale components differ significantly from the properties of the common materials used in large-scale magnetics. The dimensional constraints due to the fabrication process form a main difference as well. For the design of such devices, two- and three-dimensional numerical field modeling techniques, such as FEM, are essential. This paper discusses modeling strategies combining two- and three-dimensional FEM methods, along with circuit equations, allowing investigation of the behaviour and design of new components. Index Terms -- Finite element methods, eddy currents, micro-inductors