Index of rotor losses in three-phase fractional-slot permanent magnet machines

The aim of here is to define an index of the rotor losses induced by the magnetomotive force (MMF) space harmonics in fractional-slot permanent magnet (PM) machines. Such an index facilitates a rapid discrimination of the various fractional-slot PM machines, based on the numbers of slots and poles. For the sake of generality, a simple model of the rotor losses is adopted to compute such an index of rotor losses. However, the index behaviour follows that of rotor losses computed by means of more complex models.     

Design and implementation of a calorimetric measurement facility for determining losses in electrical machines

The measurement of the total losses of electrical machines is of most interest to designers for verifying their calculations. We show the limitations of the conventional input-output procedure leading to loss figures. An alternative method is proposed. For this purpose, a calorimetric measurement facility was designed and implemented. This paper is intended to present the calibration procedure for this facility, as well as results of tests performed on a 10 hp (7.5 kW) induction motor.     

The electromagnetic forces and losses in cryoturbogenerator rotor shells

A two dimensional model to describe the electromotive forces and losses in the shells of the cryoturbogenerator rotor cryostat is given and qualitative analysis of the results made.     

Mathematical models of synchronous electrical machines

This paper is concerned with developments in mathematical modelling of turbo-generator units for use in the dynamic analysis of electrical power systems. Emphasis is placed on an over-all reduction in computing time, whilst retaining a high order of accuracy of transient response. Accurate linear models are then derived and provide an alternative to the piecemeal formulations hitherto employed in small signal analysis. These equations form a practical basis for the synthesis of optimal control systems for large alternators.     

Closed evaporative cooling of rotating electrical machines

Elements of a theory for centrifugo-axial heat pipes are described along with a calorimetric device for their experimental investigation. Experimental data presented confirms the fundamental correctness of the initial theoretical hypotheses.     

PBSZT压电陶瓷机械损耗和介电损耗的关联性

为探索PZT压电陶瓷材料的损耗机理,对Pb0.9Ba0.05Sr0.05(Sn1/3Nb2/3)0.06(Zn1/3Nb2/3)0.06Ti0.44Zr0.4403分别进行Co2O3、Sb2O3掺杂,Mn(NO3)2、Sb2O3掺杂的实验,以及陶瓷的不同成型工艺的比较实验.该PBSZT体系在相同烧结条件下,一定量的Sb2O,Mn(NO3)2掺杂下,体系机械损耗与介电损耗之比为0.09左右;而一定量的Co2O3、Sb2O3掺杂时,则其值在0.55左右.表明一定的材料组成下,机械损耗和介电损耗有较好的相关性,但同时不同成型方法也对同一组成的两种损耗的比值影响较大.     

Review of condition monitoring of rotating electrical machines

Condition monitoring of rotating electrical machinery has received intense research interest for more than 30 years. However, electrical machinery has been considered reliable and the application of fast-acting digital electrical protection has rather reduced the attention operators pay to the equipment. The area based upon current literature and the author's experience is reviewed. There are three restrictions: only on-line techniques for rotating machines are dealt with; specific problems of variable speed drives are not dealt with, except in passing; conventional rather than emerging brushless, reluctance and permanent magnet machines of unusual topology are concentrated upon. The art of condition monitoring is minimalist, to take minimum measurements from a machine necessary to extract a diagnosis, so that a condition can be rapidly inferred, giving a clear indication of incipient failure modes. The current state of the art is reviewed in the following ways: survey developments in condition monitoring of machines, mechanically and electrically, over the last 30 years; put that work in context alongside the known failure mechanisms; review those developments which have proved successful and identify areas of research which require attention in the future to advance the subject.     

Study of the electrical discharge coating degradation

The peculiarities of formation and destruction of coatings formed by electrical discharge machining (EDM) have been investigated. The kinetic theory of solid-state strength has been used to explain the experimental data. The important role of the thermal fluctuational process in the kinetics of coating formation by EDM has been shown.     

Temperature field in the rotor of a thermally stressed electrical machine

The temperature field in the rotor of a thermally stressed high-speed electrical machine is investigated. The problem is solved on a computer by the grid method. Results of computation of the temperature field in the rotor for different conditions of cooling are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 17, No. 3, pp. 491–498, September, 1969.     

Control of rotor torque and rotor electric power of a shaft-mounted electrical load in a mixed pole machine

A new operational mode for mixed-pole machines is presented. The proposed wound reluctance rotor machine can produce an n-phase rotor electric power from the rotor windings to a resistive or inductive load, independent of rotor torque, at any desired synchronous speed. The two-stator windings, with a different number of poles, are fed from two voltage source inverters on a common dc link. This type of machine can be used in applications that require control of both rotor torque and rotor electric power, such as contactless rotational antennas and turret systems. The machine mathematical model is presented, with open- and closed-loop control systems, simulated and experimentally validated.     

Improving the signal data acquisition in condition monitoring of electrical machines

The occurrence of a broken bar in induction machines causes an internal magnetic imbalance, which is reflected in the stator current. This effect may be detected by estimating the spectral signature of the stator current, particularly the sidebands around the fundamental frequency. However, the fundamental 60-Hz amplitude is considerably greater than the sideband amplitude, which usually requires an analog 60-Hz notch filter in the data acquisition system. Analog filters are sensitive to temperature variations, which, in this case, may shift the filter resonance frequency and degrade the desired response. It is proposed in this paper that the analog notch filter may be replaced by a digital/analog cancelling technique based on the recursive discrete-time Fourier transform. The technique is shown to attenuate the fundamental 60-Hz amplitude considerably before A/D conversion, leaving only the sidebands in the current signal.     

Investigations on the mechanical behavior of a wind rotor blade subcomponent

In the present study prismatic composite I-beams, designed within the UpWind-project to examine the mechanical behavior of adhesive bond lines, are numerically and experimentally investigated. Different test set ups are used and the test results are compared. A Finite Element Model (FEM) is developed to predict and simulate the damage initiation and evolution using a progressive damage scenario. The FEM is used also as a tool to propose an alternative experimental set-up to avoid undesirable local effects. The results of the simulation are directly compared with the experimental observations coming from Digital Image Correlation Technique (DICT) and conventional techniques (Linear Variable Differential Transformers – LVDT and straingages). Finally a qualitative and quantitative analysis of the damage within the I-beam structure is performed, using results of the FEM.     

An integral equation approach to the computation of nonlinearfields in electrical machines

A numerical method based on an integral equation formulation, for the computation of nonlinear magnetostatic field, in two dimensions in cylindrical polar coordinates is given. The correctness of the method is illustrated by solving two linear two-dimensional magnetic field problems which have readily available analytical solutions. The dependence of the accuracy of the solution on the number and distribution of the meshes is studied on these examples. The method is then applied to the computation of the nonlinear field of a small salient pole synchronous machine. The technique used to accelerate the solution and other aspects of the solution are discussed. The program is used for the computation of magnetization characteristics, zero-power-factor characteristics, terminal voltages and their harmonics, and the field distribution in the air gap. Computed characteristics are compared with measurements. The results obtained illustrate that accurate and reasonably quick results are obtainable using this method     

Effect of zeolite content in the electrical, mechanical and thermal degradation response of poly(vinylidene fluoride)/NaY zeolite composites

Polymer based composites of a-PVDF doped with different NaY zeolite (Na53Al53Si139O384) content were investigated. A good dispersion of NaY zeolite within the polymer matrix is achieved. The introduction of NaY nanoparticles enhance the storage modulus and the dielectric constant at room temperature. The dielectric constant at room temperature increases up to the value of 500 for the 32 wt% composite, at 1 kHz. The increase of the dielectric constant is mainly attributed to interfacial polarization effects. For increasing zeolite content, the nanocomposite conductivity shows two conducting regimes separted by the so called breaking voltage, which is associated to an intrazeolite charge transport. Thermogravimetric results show that the introduction of zeolites affects the thermal degradation of the polymer for low zeolite contents and also indicate the presence of water that also plays an important role in the electrical response of the materials.     

Determination of efficiency losses in gas suspensions

Equations for calculating the efficiency losses in a polydisperse gas suspension which are due to chemical reactions, diffusion, thermal and mechanical interactions between phases, etc., are obtained by the methods of nonequilibrium thermodynamics.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 3, pp. 499–503, March, 1976.