Stucky a dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of master of science department. These high frequency effects are caused by the magnetic field resulting from current flow in transformer windings and circuit wiring. Relaxation effect model derivation 2 1 mittwoch, 29. To minimize the eddy currents,the metal core to be used in an appliance is taken in the form of thin sheets. Heat is generated any time current flows in a conductor. This implies that the relative importance of the eddy current losses increases with the. Magnetic eddy current inline inspection tool development. Calibration of commercial eddy current instruments for. An expression is derived for the eddy current loss of a thin transformer lamination by assuming that the permeability. These transformers are designed around cost and driving the flux very high. The highfrequency magnetic field is generated by flowing a highfrequency current to the coil inside the sensor head.
A study of frequency dependent losses in transformer. The power loss due to the flow of this current is known as the eddy current loosed. Consequently, the sum of the eddycurrent loss components associated with eachspace harmonicmay lead toan incorrect total eddycurrent loss in a magnet segment. This paper is intended to provide insight into these phenomena so that improved high fre. Various methods are used to minimise eddy current losses in the core end regions. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.
The paper deals with eddy current losses in transformer low voltage foil coils, where the measured value of the load loss is usually much higher than the one computed by standard procedures. These eddy currents act against the externally applied magnetic field, causing decreased flux and increased losses as the frequency is increased. Diffusion effects in eddy current nondestructive evaluation by paul a. This is the basis of eddy current testing, by monitoring the voltage across the coil in such an arrangement we can detect changes in the material of interest. Butterworth, s philosophical transactions of the royal society of london. To address this gap in commercial ili technology, exxonmobil and innospection ltd. Pdf eddy current separation of fine nonferrous particles. Eddy current losses on the opposite hand are affected by the flow of flowing currents evoked into the steel caused by the drift of the magnetic flux round the core. Modeling high frequency eddycurrent losses inconductingcorematerials,currentsareinducedwhichflow in loops.
Eddy current losses in transformer windings and circuit wiring. These losses arise from the fact that the core itself is composed of conducting material, so that the voltage induced in it by the varying flux produces circulating currents in the material. This is within the range of current densities tested, in which the. The complete model is conceived as a spice subcircuit which includes the coil leakage inductance, the winding resistance, the eddycurrent effect. The model parameters of the preceding section have been used.
Magnetodynamic formulation resolving eddycurrent effects in the. The origins of the losses and the merits and pitfalls of traditional approaches to separation into classical eddy current and hysteresis components are. Computer based eddy current test instrument manufactured by highline automation. Copper losses are predominate, so fewer turns heavier turns lower loss. Now if f is the number of cycles of magnetisation made per second, then hysteresis lossm 3 area of one hysteresis loop x f joulessecond or watts. Konrad 4 discusses eddy currents generally in some detail and zhu, hui, and ramsden. Eddycurrent loss in rotor and pms in bldc motors, iron loss appears not only in the stator but also in the rotor. Found in ieee power electronics specialists conference, june 2004, pp. Hysteresis and eddycurrent losses of a transformer. Siow2 1faculty of mechanical engineering universiti malaysia pahang. They can be induced within nearby stationary conductors by a timevarying magnetic field created by an. Work done unit volume wm 3 area of the hysteresis loop in joules. Computation of single phase distribution transformer. The hysteresis losses per cycle are usually assumed to be independent of frequency, while the classical eddy current losses increase proportional with the frequency.
Also, the material is produced as a thin ribbon, rather than laminations, so eddy losses are practically nonexistent. The following lemma shows that the eddy current is independent of the particular form of. Regional engineering postgraduate conference epc 2011 eddy current braking study for brake disc of aluminium, copper and zink m. The metal grains are microscopic, which keeps the hysteresis losses very low. The eddy current loss density after the motor revolves one sector angle. Eddy current losses the term eddy currents is applied to those electric currents which circulate within a mass of conducting material when the latter is situated in a varying magnetic field. Several other methods such as remote field testing rft, flux leakage and barkhausen noise also use this principle. In order to reduce these losses and correspond heating of the core to small value the. Simplified highaccuracy calculation of eddycurrent loss. From the results it also can be seen that the winding ac losses which include both dc losses and eddy current losses, are 35% higher than dc losses at nominal speed of 180 rpm 63 hz. The work brings results explaining analytically the. The magnitudes of eddy current are often decreased by creating core resistance as high as sensible.
Capturing eddy current losses in a permanent magnet motor. The eddy current method utilizes highfrequency magnetic fields. The copper loss of an inductor can be calculated by multiplying the square of the current in the inductor by the resistance of the winding i 2 r. Dielectric losses attenuation reduction of the signal energy due to the substrate mostly due to the tan or dissipation factor df of the substrate conductor losses conductor losses are due to several factors. The diagram model is based on analog lumped equivalent circuits and the implementation procedure uses the principle of modularity.
The amount of heat generated is also proportional to the resistance of the conductor. In addition to copper loss, an ironcore coil inductor has. Eddy current displacement sensors measurement library. The core resistances are often greatly exaggerated by making the core of skinny, spherical iron sheets referred to as laminations shown in the fig. The planes of these sheets are arranged parallel to the magnetic field so that they cut across the eddy current paths. Eddycurrent loss in the rotor magnets of permanentmagnet. Eddy current loss depends upon the rate of change of. Practical measurements of dielectric constant and loss for. What is eddy current loss and how can we reduce it. Copper surface roughness dc and ac resistance of the.
Investigation of volumic permanentmagnet eddycurrent losses in. The effects of eddy currents in transformer windings are considered, and a method is derived for calculating the variation of winding resistance and leakage inductance with frequency for transformers with singlelayer, multilayer and sectionalised windings. These flowing currents are generated as a result of to the magnetic flux the core is performing sort of a single loop of wire. How hysteresis losses in a transformer core can be reduced. Eddy current separation, in addition to electrostatic separation 88, 89, can be useful for concentration of nonferrous metals like cu or al from the waste particle sizes between 2 and 50 mm 90. Eddy current losses in mnzn ferrites article pdf available in ieee transactions on magnetics 501. The method consists in dividing the winding into portions, calculating the d. The highorder magnetic flux density harmonics, which are not synchronous with the rotor, cause those parasitic eddycurrent losses in the pms 5. Hysteresis losses, eddy current losses and copper losses. Eddy currents also called foucaults currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to faradays law of induction. Note that cracks must interrupt the surface eddy current flow to be detected. This loss could be considerable if solid iron core were used. Highfrequency resistivity of soft magnetic granular films.
The last one is the actual question that i need to be answered. Since the magnetic material is a conducting material, these emfs circulates curr. This power is wasted power and is called copper loss. The highline automation ec14 has a frequency range of 40hz to2 mhz the instrument will meet or exceed the requirements of appendix a. Formulation of the eddy current problem in hysteretic. Copper loss is an i 2 r loss, which increases as current increases. Eddy current losses in soft magnetic materials wiley.
I am having problems with the following question if anyone can assist an eddy current inspection method is being used to measure the thickness of 7075t6 aluminium sheets electric conductivity is 1. Modeling and analysis of eddy current losses in permanent. Diffusion effects in eddy current nondestructive evaluation. Consequently, the magnitude of eddy current and therefore eddy current loss are massive. The resistance of the conductor varies directly with its length and. Accurate timedomain simulation of nonlinear inductors. Eddy current inspection is one of several ndt methods that use the principal of electromagnetism as the basis for conducting examinations. In this work the hysteresis loss, particle eddy current loss and component bulk eddy current loss of smc magnetic cores are analysed with the. The instrument is a dual channel dual frequency instrument. In this case the iron losses are purely the eddycurrent losses. When an alternating magnetic field is applied to a magnetic material an emf is induced in the material itself according to faradays law of electromagnetic induction. If a measurement target metallic is inserted into this magnetic field, electromagnetic induction causes magnetic flux to pass over the surface of the object and.
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