Magnetic loss

Core losses or magnetizing losses, which comprise... 

Magnetizing losses, however, as the name implies, are a phenomenon in electromagnetic circuits only. They are absent in a non-magnetic circuit. A motor is made of steel laminates and the housing is also of steel, hence these losses. Some manufacturers, however, use aluminium die-cast stator frames in smaller sizes, where such losses will be less (the bulk of the losses being in the laminations). 

Remain constant for speed variations within the required speed N, as the field current is kept fixed and only the armature voltage is varied. For speed variations beyond N. however, when the armature voltage is kept constant and the field current is varied, the magnetizing losses afso vary... 

No reduction becau.se of same magnetizing losses and therefore relatively higher /]... 

If there are N number of CTs connected in parallel, the magnetizing current will flow through all of them. In a CiF protection scheme all the three CTs of all the feeders being protected together will fall in parallel, while in case of a combined GF and phase fault protection scheme, only one third of these CTs will fall in parallel. The CT in the faulty circuit must be able to draw enough current to feed the magnetizing losses of all the CTs falling in parallel and the relay pickup current, The sensitivity of the differential scheme can therefore be expressed more appropriately as... 

If the heal generated by induced currents (there are no magnetic losses) on load on per phase basis is In the main conductor, due to I, = - I , ... 

Chemical reagents are primarily concerned with dielectric liquids or solids. For metal oxides such as ferrites, however, magnetic losses occur in the microwave region. As for a dielectric material, a complex magnetic permeability is defined as given by Eq. (16) ... 

The real part is the magnetic permeability whereas the imaginary part is the magnetic loss. These losses are quite different from hysteresis or eddy current losses, because they are induced by domain wall and electron-spin resonance. These materials should be placed at position of magnetic field maxima for optimum absorption of microwave energy. For transition metal oxides such as iron, nickel, and cobalt magnetic losses are high. These powders can, therefore, be used as lossy impurities or additives to induce losses within solids for which dielectric loss is too small. 

Consequences of the thermal changes of the dielectric permittivity 1 Conduction losses 13 Magnetic losses 13... 

Irradiation of a sequence of very short resonant RF-pulses with a sum of pulse angles of 0° for on-resonant spins. Spin ensembles with long Tj show nearly full longitudinal magnetization after the pulse sequence. Spin ensembles with short T2 get severe transverse magnetization loss between and during the pulses and therefore is clearly reduced after application of the pulse sequence (e.g., Ref 44). 

Soft ferriles have a slender S-shaped hysteresis loop with low rcntanencc and low ciicreivc force permitting easy magnetization and demagnetization with little magnetic loss. These ferrites are uniquely suited to low-ioss inductor and transformer cores for radio, television, and carrier telephony. 

Eq. (9.20) shows that, for a small gap and at low field strengths, the ratio (tan 5)/ p of a high-permeability low-loss material is independent of the gap width and is therefore a useful material constant in the pot-core context. It is often referred to as the magnetic loss factor but is clearly quite different in character from the dielectric loss factor (see Section 2.7.2). It indicates that a reduction in permeability due to the introduction or enlargement of a gap is accompanied by a proportionate reduction in tan (5m (or increase in Qm). 

The way in which magnetic loss in a material is expressed depends upon the particular application. For example, in the case of pot cores, when currents are small and hence the flux density is also small (typically less than 1 mT), the loss factor used is (tan <5)//iri or its reciprocal jinQ where Q is the quality factor. 

The iron losses arise in the armature stampings and consist of eddy current losses and magnetic losses. To reduce eddy currents, the poles are manufactured from laminated material. Magnetic losses are determined by the choice of material. 

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