[en] Flux pumps have been investigated for a number of years as a means of powering large magnets. In this paper a simple system consisting of one, or two, loops under a moving magnet is analysed theoretically. It is a circuit model using only Faraday’s law of induction and the V–I characteristic. However in contrast to distributed systems with tapes or sheets, the performance can be calculated from first principles and the results expressed in a few simple formulae. With one loop and a constant I _c no significant flux pumping occurs if the n value is large. However if I _c is a function of B the saturation current is approximately I _c1–I _c2 where these are the critical currents in zero field and under the magnet respectively. Nearly all the magnet flux is transferred in each cycle so the number of cycles needed to reach saturation is about 2(I _c1–I _c2) L ₂/ϕ where L ₂ is the inductance of the load magnet and ϕ the flux of the moving magnet. The loss is ϕI _c joules on each pass and the mean loss about ϕI _c /T watts, where T is the time of a pass. Adding another loop makes an even better flux pump even if I _c is constant. Now the saturation current is I _c and the number of cycles about 2I _c L ₂ /ϕ. If the current starts above the saturation value it decreases to saturation over a similar number of cycles, more of a ‘flux suck’ than a flux pump. (paper)

No abstract available

[en] This paper describes an improved method for the modeling of axial and radial eccentricities in induction motors (IM). The model is based on an extension of the modified winding function approach (MWFA) which allows for all harmonics of the magnetomotive force (MMF) to be taken into account. It is shown that a plane view of IM gets easily the motor inductances and reduces considerably the calculation process. The described technique includes accurately the slot skewing effect and leads to pure analytical expressions of the inductances in case of radial eccentricity. In order to model the static, dynamic or mixed axial eccentricity, three suitable alternatives are explained. Unlike the previous proposals, the discussed alternatives take into account all the harmonics of the inverse of air-gap function without any development in Fourier series. Simulation results as well as experimental verifications prove the usefulness and the effectiveness of the proposed model.

[en] The paper deals with the self-induction of two parallel infinitely long conductors of arbitrary cross section connected to an ideal sinusoidal voltage source. The conductors do not move. A quasi-stationary behavior is assumed, the displacement current is neglected and the permeability of the conductors and their surroundings equals the permeability of vacuum. The subject matter of the paper is the calculation of impedance, which in the theory of circuits with lumped elements can replace 1 m of conductors. The definition of inductance and the formulae for its calculation that form part of textbooks on physics and electromagnetism have been the same for such a long time that nobody doubts their correctness. Only the recently published method for the calculation of current density in long parallel conductors allows calculating accurately the equivalent impedance and self-inductance, and also evaluating critically the present knowledge. (paper)

[en] We study a system of two RLC oscillators coupled through a variable mutual inductance. The system is interesting because it exhibits some peculiar features of coupled oscillators: (i) there are two natural frequencies; (ii) in general, the resonant frequencies do not coincide with the natural frequencies; (iii) the resonant frequencies of both oscillators differ; (iv) for certain choices of parameters, there is only one resonant frequency, instead of the two expected

[en] The results of development, manufacturing and testing of a special contactless maintenance-free excitation current measurement system intended for the windings with high inductance, typical for superconductive alternators, are presented. The system was assembled on the brushless exciter is intended for 1 MVA wind-power generator with the winding, manufactured of high-temperature superconductors (HTSC). The alternator with brushless exciter were manufactured and successfully tested. (paper)

[en] This paper presents the numerical modeling (using the Finite Difference Method-FDM, and Finite Element Method- FEM) of the electromagnetic and thermal fields in a steel piece heated up inside an induction crucible furnace, and the experimental validations. Both modeling have been validated experimentally, so they can be used in designing the equipment and in the numerical control of induction heating process. The program based on FDM can be used in the first stage of designing due to the reduced CPU time. In this stage the inductor parameters and heating time can be estimated, and a study of the influence of diverse factors upon the heating process can be achieved. The FLUX 2D program can be used in the optimization stage, because it allows a more thorough analysis of the phenomena. (Author) 29 refs

[en] A stator malfunction occurs due to insulation damage, which means that the stator is directly connected to the power supply, and a direct connection is the direct cause of a major accident. For this reason, a lot of research is being done to identify faults. In recent years, studies on Motor Electrical Signature Analysis are being performed, sensorless methods for fault diagnosis of the stator of an induction motor. However, it has problems with it, it has the difficulty in interpreting multi-faults and in detecting an inter-turn short circuit of a stator. This paper suggested a tool that can diagnose 2-turn short circuit, through the relationship between self-inductance and mutual inductance in the synchronous reference frame of a D-Q transformation. (paper)

[en] Introductory electromagnetism courses usually start the exposition of Faraday's induction law discussing the ordinary situation in which the induced electromotive force arises due to the motion of a resistive circuit in the presence of a magnetic field. In this paper we extend the discussion to cover the application of Faraday's law to perfectly conducting as well as to superconducting circuits rather than resistive circuits. While in resistive circuits the work done by the external agent is transformed into heat, the situation is quite different in either perfectly conducting or superconducting circuits. In superconducting circuits the work done by the external agent is used to accelerate the charge carriers, and magnetic energy is transferred from the magnet's magnetic field to the circuit where it is stored in the trapped field. The total flux trapped inside a perfectly conducting circuit is initially conserved but decays with time. In superconducting circuits what is conserved is a quantity called 'fluxoid'. The overall problem is very instructive since it employs the concept of self-inductance also, and it may be used to increase the student's interest on the important topic of superconductivity

[en] Role of self-inductance in superconducting quantum interference device (SQUID) charge qubit is considered. It is found that when an SQUID charge qubit is coupled to a quantum LC resonator, the SQUID voltage operator equation is modified in accompanying with the modification of operator Faraday equation describing the inductance. It is shown that when the extra energy is applied to the junction, the mean phase will be squeezed according to a damping factor