Hysteresis loss


The properties for head materials can be summarised as large saturation magnetisation for produciag a large gap field, high permeabiHty at all frequencies ia order to ensure high efficiency, small coercivity with low hysteresis loss, low magnetostriction for obtaining low—medium contact noise, and small but not sero magnetic anisotropy to suppress the domain noise. To ensure good reHabiHty and a long operating time, the head materials must exhibit a good thermal stabiHty and a high resistance to wear and corrosion. The choice of materials and preparation technologies are the tools for tailoring head and medium properties.  [c.171]

Silicon Steel Electrical Sheets. The siUcon steels are characterized by relatively high permeabiUty, high electrical resistance, and low hysteresis loss when used in magnetic circuits (see Magnetic materials). First patented in the United Kingdom around 1900, the siUcon steels permitted the development of more powerful electrical equipment and have furthered the rapid growth of the electrical power industry. Steels containing 0.5—5% siUcon are produced in sheet form for the laminated magnetic cores of electrical equipment and are referred to as electrical sheets (54).  [c.400]

Xanthogen disulfide modified polymers are a close relative of the mercaptan modified polymers in that polymer molecular weight is determined during polymerization. They differ in that polymer modified with a xanthogen disulfide has cure reactive end groups (142,143). As a result, vulcanizates from xanthate modified polymers have better utilization of chain ends and a generally tighter cure. This results in improved tensile properties and reduced hysteresis loss and creep. The downside is that sulfur residues from this chemistry impair the heat resistance of vulcanizates. Depending on chain-transfer kinetics for particular mercaptans and xanthogen disulfides, the xanthate modified polymer may have a broader molecular weight distribution, and, for that reason, improved processibiUty (110,143).  [c.545]

Figure 1.10 Hysteresis loop and magnetizing curve illustrating hysteresis loss Figure 1.10 Hysteresis loop and magnetizing curve illustrating hysteresis loss
Core loss is the magnetizing or hysteresis loss and represents the iron loss of the machine.  [c.263]

For MS enclosures, which will have both hysteresis loss B and eddy current loss a higher derating factor must be  [c.874]

The eddy current loss is a much smaller loss than the hysteresis loss, but increases significantly with the operating frequency. It is shown in Equation 4.7.  [c.140]

Physical properties of the different systems are listed in Table 3. The m-EPDM-DCP system (mix EPO) was cured to the same level as the m-EPDM-ZnO (mix EPl) by choosing molding times so that the torque increase (i.e., the difference between the maximum torque and the minimum torque) is the same in both cases. As compared with the m-EPDM-DCP system, the m-EPDM-ZnO system shows higher hardness, modulus, tensile strength, and tear resistance presumably due to the presence of ionic clusters, which will be discussed later. The higher elongation at break in the m-EPDM-ZnO system is believed to be due to the occurrence of stress-induced ion exchange, which causes lowering of stress concentration, resulting in high elongation [21], Hysteresis loss follows the order EPO < EPl < E-P2 < EP3. Hysteresis of the ionic system (EPl) is higher than the DCP cured system (EPO). Reinforcing fillers, in general, are known to cause an increase in hysteresis of rubbers. Accordingly, it is believed that the ionic aggregates in the m-EPDM-ZnO system act not only as crosslink sites, but also as fillers providing reinforcement to the matrix [22]. The effect becomes more pronounced on addition of stearic acid and zinc stearate. Incorporation of stearic acid facilitates formation of ionic aggregates. It has been reported that at ambient conditions crystalline zinc stearate acts as a reinforcing filler in metal oxide crosslinked carboxylic rubbers [23], Results of measurements of physical properties at 70°C reveal that the reinforcing ability of zinc stearate diminishes at higher test temperatures, presumably due to the onset of melting of zinc stearate and the consequent plasticization.  [c.442]

Although not fully understood, contact line hysteresis is generally attributed to surface roughness, surface heterogeneity, solution impurities adsorbing on the surface, or swelling, rearrangement or alteration of the surface by the solvent. The local tilting of a rough surface or the local variation in interfacial energies on a heterogeneous surface can cause the contact angle to vary. It is not yet clear whether, like other hysteretic phenomena (such as found in magnetism), contact angle hysteresis can be described by irreversible transitions or jumps between domains of equilibrium states [41]. Here we review some of the main features of heterogeneous or rough surfaces and their effect on contact angle measurements.  [c.355]

The situation is complicated, however, because some of the drag on a skidding tire is due to the elastic hysteresis effect discussed in Section XII-2E. That is, asperities in the road surface produce a traveling depression in the tire with energy loss due to imperfect elasticity of the tire material. In fact, tires made of high-elastic hysteresis material will tend to show superior skid resistance and coefficient of friction.  [c.438]

The hydration shell is formed with the increasing of the water content of the sample and the NA transforms from the unordered to A- and then to B form, in the case of DNA and DNA-like polynucleotides and salt concentrations similar to in vivo conditions. The reverse process, dehydration of NA, results in the reverse conformational transitions but they take place at the values of relative humidity (r.h.) less than the forward direction [12]. Thus, there is a conformational hysteresis over the hydration-dehydration loop. The adsorption isotherms of the NAs, i.e. the plots of the number of the adsorbed water molecules versus the r.h. of the sample at constant temperature, also demonstrate the hysteresis phenomena [13]. The hysteresis is i( producible and its value does not decrease for at least a week.  [c.117]

These results allows us to connect the observed hysteresis to the conformational changes in the NA molecule and consider it not as a macroscopic phenomenon like capillary hysteresis, but as natural property of the NA-water system. Our experimental and numerical results are in agreement with the data of other authors [13], [12], [14].  [c.122]

Following Zsigmondy, early workers in the field assumed the pores to be cylindrical and the angle of contact to be zero, so that the meniscus was hemispherical. The mean radius of curvature r thus became equal to the radius of the pore less the thickness of the adsorbed film on the walls. By application of the Kelvin equation it was therefore possible to calculate the minimum radius of pores in which capillary condensation can take place, from the relative pressure at D, the lower limit of the hysteresis loop. General experience from the time of Anderson (working in Zsigmondy s laboratory) onwards, shows that this minimum radius varies from system to system, but is rarely below 10 A. The upper limit of the applicability of the Kelvin equation, r 250 A, is a practical one, set by the experimental difficulty of measuring very small lowerings of vapour pressure (cf. Table 3.8). The justification for defining mesopores by reference to the limits 10 to 250 A therefore rests on the fact that the classical capillary equations, especially the Kelvin equation, are applicable in this range.  [c.113]

Both the cone-shaped and the wedge-like pore give rise to simple, hysteresis-free behaviour. The meniscus is nucleated at the apex of the cone (Fig. 3.14(a)) or at the intersection of the two planes of the wedge (Fig. 3.14(b)), giving a spherical meniscus in the first case and a cylindrical one in the second. In both systems the process of evaporation is the exact reverse of that of condensation, and hysteresis is therefore absent.  [c.129]

In formulating an explanation of this enhanced adsorption, there are several features to be accounted for the increase in adsorption occurs without hysteresis the amount of adsorbate involved is relatively small the Kelvin r -values are also small (e.g. for nitrogen, less than 17 A) and the effect is found in a region of relative pressures where, according to the simple tensile strength hypothesis, capillary condensate should be incapable of existence.  [c.163]

Since by definition r is less than r , the pressure P, for intrusion will be greater than that for extrusion, P , and there will be hysteresis.  [c.184]

As pointed out earlier (Section 3.5), certain shapes of hysteresis loops are associated with specific pore structures. Thus, type HI loops are often obtained with agglomerates or compacts of spheroidal particles of fairly uniform size and array. Some corpuscular systems (e.g. certain silica gels) tend to give H2 loops, but in these cases the distribution of pore size and shape is not well defined. Types H3 and H4 have been obtained with adsorbents having slit-shaped pores or plate-like particles (in the case of H3). The Type I isotherm character associated with H4 is, of course, indicative of microporosity.  [c.287]

Friction and Ultrasonic Welding. Both rotational and linear friction can be used to melt the interface between two thermoplastics. The parts are then aligned, and a weld is formed as the interface solidifies. Linear friction welding, also called vibration welding, employs frequencies in the 100—500 Hz range welding can be accompHshed in less than one second but is limited to bond areas approximately 400 mm. Ultrasonic welding of polymers involves oscillations of 10—50 kH2, which are dissipated at the bond line to produce heat through both friction and hysteresis. The surfaces to be joined are held together as the sound energy generated by the welding machine is transferred through the parts at right angles to the contacting surfaces. Like the friction process, ultrasonic welding is limited to smaller part sizes.  [c.345]

Ferrites aHowing for operation at frequencies well above 1 MH2 have also become available, eg, 3F4 and 4F1 (Table 6). Other newer industrial power ferrites are the Siemens-Matsushita N-series (28,97) the TDK PC-series (28,100), and the Thomson B-series (28,103). While moving to higher frequencies, the ferrites have been optimized for different loss contributions, eg, hysteresis losses, eddy current losses, and resonance losses. Loss levels are specified at 100°C because ambient temperature in power appHcations is about 60°C plus an increase caused by internal heat dissipation of about 40°C.  [c.197]

Like most materials, glass expands when it is heated and contracts when it is cooled. If the thermal cycling is slow enough, there is virtually no hysteresis effect. Linear expansion, AL/L-, is the change in length pet initial length. Generally, the expansion is proportional to temperature up to 300°C or more, depending on the glass. The slope of the linear expansion vs temperature curve, the linear thermal expansion coefficient, a, is therefore virtually constant between 0 and 300°C for most glasses, and thus CCq qq is a useful property for comparisons (see Table 4). As the temperature of the glass rises to neat the set point (strain point +5° C), the thermal expansion increases more rapidly (compare Figure 1, which is a volume—temperature curve for a general glass). The volume—temperature curve is analogous to linear expansion (length—temperature) curves. The density, p, which depends on the temperature, is easily calculated from the density at room temperature and the appropriate linear thermal expansion coefficient.  [c.297]

Processing and Properties. Sulfur vulcanization is generally used with higher accelerator levels, as in the case of EPDM. Unlike EPDM, this elastomer has sufficient chain regularity to permit crystallization on stretching so it can exhibit high gum strength. However, its low modulus requires carbon black for stiffening, not for strength. Butyl mbber has a T of —72° C, but has a broad loss peak thus it shows low resilience at room temperature, with a high hysteresis loss. It is therefore a useful damping mbber. Butyl mbber is remarkable for its excellent impermeability to gases, which led to its widespread use for inner tubes for tires, and more recentiy for the barrier in tubeless tires. It cannot be blended with high unsaturation mbbers in sulfur vulcanization. However, its halogenated derivatives, chlorobutyl and bromobutyl, can be covulcanized with the unsaturated elastomers, eg, SBR in tubeless tires, because of the interaction with the zinc oxide in the compound.  [c.469]

See the curve abcda in the shape of a loop, whieh is drawn at different values of H after the magnetic core was magnetized up to its saturation level on. This is known as a hysteresis loop and the magnetic area represented by daehd as the energy stored. This energy is not released in full but by only a part of it (bae) back to the magnetizing circuit when the magnetic field H (or eurrent) is reduced to zero. The loss of this energy (dab) is termed hysteresis loss and appears as heat in the magnetizing circuit, i.e. the stator and the rotor of an induction motor. This loss may be attributed to molecular magnetic friction (magnetostriction) and is represented by  [c.13]

In fad. ihis energy should be less by the hysteresis loss (Seetion l.6.2A.(iv)) whieh has been ignored in the present analysis. If T, is the prospeetive peak surge voltage (TRV) in volts and C the dieleetrie eapaeitance of the eontaet gap in far.id at the instant of restrike, then the eapacitive energy J, received across the contact gap is  [c.649]

A hysteresis loss in an electromagnetic circuit will occur due to molecular magnetic friction (magnetostriction), as discussed in Section 1.6.2(A-iv). This causes a distortion in voltage and current by distorting their natural sinusoidal waveforms. This distortion in the natural waveforms, in terms of magnetizing current 1, induced e.m.f. e and magnetic flux 0 of the magnetic circuit is the source of generating triple harmonic quantities, the magnitude of which will depend upon the shape of the hysteresis loop, which is a function of the core material. A Huctuation in the system voltage which causes a change in the flux density B (equation (1.5)) also adds to the triple harmonic quantities. Permeability ju of the magnetic core is different at different flux densities B. This results in giving rise to triple harmonics due to magnetic friction (magnetostriction). Wherever the switching of a capacitor bank is more frequent, the generation of triple harmonic voltages is more severe.  [c.740]

The spinel and magnetoplumbite magnetic materials differ considerably in behaviour, and therefore have different applications. The spinels are soft magnets which respond rapidly to changes in the direction of the magnetizing field, H, and hence have a naiTow B-H curve where B is the induced magnetization, and are useful in transformer coils. The magnetoplumbites on the other hand are hard magnets which show a broad B-H curve, indicating a high hysteresis loss and are used in loudspeakers and other permanent magnet applications where die retention of magnetization is necessary over a period of time. Finally tire garnets are used extensively in microwave circuits where the flexibility of design of the magnetic properties which accompanies the variation in the rare-eartlr ion composition can be usefully applied.  [c.239]

There are three major losses assoeiated with transformers and induetors hysteresis loss, eddy eurrent loss, and resistive loss. These losses are eontrolled during the transformer or induetor s design and eonstruetion.  [c.140]

The hysteresis loss is eaused by the amount of turns plaeed upon the eore by the driving eireuit. This dietates how large an area within the B-FI eurve is swept out during eaeh cyele of operation (see Figure D-3 in Appendix D). The area swept out by the operating minor-loop is the amount of work that is required to apply foree to the magnetie domains within the eore and some of them remain reoriented (residual flux density). The larger the area swept out, the more hysteresis loss. The loss is given by Equation 4.6.  [c.140]

The major losses within any core material are the hysteresis loss and eddy current loss. These losses are typically lumped together by the core manufacturer and given in a graph of watts lost per unit volume V5. the peak operational flux density (5max) and frequency of operation. Hysteresis loss is given as  [c.236]

A pseudo reaction coordinate can be obtained by fixing one of the parameters and allowing the rest of the geometry to optimize. The fixed parameter is then stepped along the path and the rest of the structure reoptimized at each step. This is also called a trial reaction coordinate. This algorithm does not yield a rigorously correct MEP. This is because the chosen parameter may be the one moving the farthest at some points along the path, but not at others. The resulting MEP will look reasonable when the parameter gives a good description. When the parameter poorly describes the MEP, a very small change in the parameter value might result in a very large change in energy and geometry. Thus, the pseudo reaction coordinate will find energies on the MEP, but will locate them at an incorrect distance along reaction route. A poorly chosen reaction coordinate will sometimes result in a hysteresis in which a different IRC is obtained by increasing the reaction coordinate rather than by decreasing it. In this case, the geometries obtained will not be exactly those along the true IRC, although they are often close. Some software packages have an automated version of this algorithm called a coordinate driving algorithm.  [c.160]

In the compaction studies described in Section 3.1, it was found that the Type IV isotherm obtained with the compact was almost coincident, in the pre-hysteresis region, with the Type II isotherm of the uncompacted powder. It follows that the BET area will likewise be unchanged by compaction, for it is this region which gives rise to the BET plot. In the experiments of Fig. 3.4, for example, the BET area of the alumina was still 96 m g after compaction at 1480GNm (96tonin ) as compared with the value 98m g" for the loose powder—a very small reduction, readily explicable in terms of slight loss of area and accessibility around points of contact of neighbouring spheres. (With softer materials such as silica, the specific surface is reduced significantly at sufficiently high compaction pressures.)  [c.168]

A difficulty in using the method is that of identifying the ptoint F, where capillary condensation commences. This is usually taken as the lower closure point of the loop but as was pointed out in Section 3.5, capillary condensation can occur without hysteresis if the pores are of an appropriate shape—such as wedge-like—before the irreversible condensation responsible for the hysteresis loop sets in. The uncertainty arising from this cause is considerable, since the curve of ln(p°/p) is very steep in this region (cf. Fig. 3.28).  [c.171]

In Chapter 3, the effect of mesoporosity in converting Type II into Type IV isotherms was discussed by reference to experiments in which nonporous powders were compacted so as to produce mesoporous solids. Analogous experiments demonstrating the conversion of Type III into Type V isotherms are lacking, but other, slightly less direct, evidence is still available. Thus Kiselev has measured the isotherms of n-pentane on several varieties of silica. The different isotherms, reduced to a common basis by plotting the adsorption per unit area (as determined, presumably by nitrogen adsorption) are shown in Fig. 5.7. Curve A refers to quartz and pyrex glass which are virtually nonporous, and curve B to silica gel having pore openings of diameter around 1(X)A (cf. Chapter 3). The two curves agree excellently up to the point where the hysteresis loop commences for  [c.258]

At high frequencies ferrites exhibit energy losses resulting from various physical mechanisms at different frequencies and appearing as heat dissipation. Hysteresis losses arise from irreversible domain wall jumps. During each cycle of the JT- and E-ftelds one hysteresis loop is completed and the loss per cycle is proportional to the area of the loop. A way to reduce hysteresis losses, ie, prevent domain wall jumps, is to reduce the number of inhomogeneities able to pin domain walls, eg, pores and impurities, and to reduce magnetocrystalline and stress anisotropy (51,52). Another method is to dehberately pin the walls, for instance by addition of Co and Ti ions or by using ceramic microstmctures having small grains (53,54). A second important loss contribution comes from eddy currents, induced by alternating magnetic fluxes. This contribution can be limited by providing a high electrical resistivity (55,56). At high frequencies this is not easy at all, because insulating grain boundaries tend to become short circuited as a result of the permittivity of the ferrite (28). A third main loss contribution is from magnetic resonances. Above about 1 MHz this is usually the dominant contribution. When the driving frequency is in resonance with the natural frequency at which the magnetization rotates, there is a large peak in power absorption. This effect can be seen when the magnetic permeabiUty is considered as the complex parameter ji = ji jji. The ratio ]l is usually expressed as tan 5, where 5 is the so-called loss angle, the phase-lag of the magnetic induction with respect to the appHed magnetic field. For inductors in electrical circuits, 5 expresses the phase difference between voltage and current. Figure 5 shows ]l and ]l" as functions of frequency for some commercial ferrites. These ferrites show large differences concerning the frequencies where ]l" starts to come up and accordingly, in the resonance frequencies, where tan6 = 1. But also the low frequency permeabiUties differ. The resonance frequency is inversely proportional to the low frequency permeabiUty (58). Applying this, shifting resonance to high frequencies can be realized by small grain sizes. The ferrites of Figure 5 are optimized for a range of frequencies and induction levels (57).  [c.190]

There are two main models from the microstmctural point of view, namely the particulate and the continuous microstmctural model. In the first one the crystals that are formed during film deposition are beheved to interact only through magnetostatic interaction. No exchange force acts over the column boundaries due to physical separation. In the continuous model the reversal mechanism is thought to take place by Bloch walls as in stripe domains, hindered by the column boundaries which can increase the coercivity of the medium. This has been studied at length for Co—Cr films having a perpendicular anisotropy (37). Several methods have been used for studying the magnetization process by experiments based on microscopic observations like magnetooptical Kerr microscopy, bitter technique, coUoid-sem method, neutron depolarization, Lorentz electron microscopy, and magnetic force microscopy on the one hand, but on the other macroscopic analysis has also been appHed by studying the various parameters of the hysteresis loop (measured with a vibrating sample magnetometer) and also the angular dependence of the appHed field. Several groups have conducted research in the field of micromagnetic simulations. Studying the intrinsic domain stmctures can contribute to the understanding of the reversal process involved.  [c.177]

Such materials caimot be used for low noise recording because for sharp transitions (no zigzag configuration) it is necessary to avoid exchange coupling between the magnetic units (grains, columns, particles) and to lower the magnetostatic interactions. Furthermore, reversal by domain-wall motion, even in a real particulate medium, acts as a noise source. Consequentiy small nonexchange coupled single-domain grains must be designed. The relation between the appHed field and the magnetization for a magnetic recording medium is given by the hysteresis loop. Such a relation is measured macroscopically by a vibrating sample magnetometer and only gives information about the average magnetic properties of the thin film. Parameters like fj, Af, L, OR, and S can be obtained from the loop and give characteristic information for recording media. Due to the small bit size in a medium it is also interesting to understand the magnetic characteristics on a small scale.  [c.177]

For alloys that usually are cooled from high temperature to room temperature, the fee y-phase exists from ca 30—100% Ni. In the low nickel regime, the y-phase undergoes a martensitic transformation to the bcc a-phase with considerable hysteresis. Of prime importance to the magnetic behavior, however, is the appearance of the long-range-ordered Cu Au-type LI2 stmeture near the Ni Fe composition below ca 500°C. The principal magnetic parameters in the Ni—Fe system are illustrated in Figure 4. The most pronounced effect of the LI2 ordering is a large change in the value of making it less positive or more negative as indicated by the dashed slowly cooled curve in Figure 4. The highest initial permeabiUty in the Ni—Fe system occurs in the 78.5% Ni alloy, but rapid cooling below 600°C is necessary. Magnetic theory indicates that high permeabiUty is achieved by minimising and This occurs for the 78.5% Ni alloy in the quenched condition. If the alloy is cooled slowly, ordering sets in, becomes highly negative, and the permeabiUty is degraded severely. With the addition of molybdenum, the kinetics of ordering is slowed and simultaneous attainment of 2ero and X is possible with moderate cooling. In this way, alloys of ca 4 wt % Mo and 79 wt % Ni reach very high values of permeabiUty. The addition of molybdenum also has the beneficial effect of increased resistivity (lower eddy-current loss) but at the expense of lower saturation induction and Curie temperature.  [c.371]

Sijua.re-Loop Alloys. Three classes of square-loop Ni—Fe alloys have been developed. In one class (50 wt % Ni), squareness is obtained through the development of cube texture, 100 (001), in the sheet. The texture results from extensive rolling (>95%) followed by primary recrystallization at ca 1100—1200°C. The use of cube texture to square the hysteresis loop also is possible in the 79 wt % Ni alloys, but the composition and heat treatment must be chosen such that > 0, ie, (001) is an easy axis of magnetization. The most recendy developed class of square-loop alloys, which are centered around 65 wt % Ni, are characterized by a squareness that is like that of the 50 wt % Ni alloy and superior to that of the 79 wt % Ni alloys and by a saturation induction that is intermediate between the two. Representative hysteresis loops are illustrated in Figure 1 the magnetic properties are given in Table 4. The 3 wt % Mo—65 wt % Ni alloy (Mo is added for increased resistivity) is unoriented, and squareness is obtained by annealing in a magnetic field.  [c.373]


See pages that mention the term Hysteresis loss : [c.13]    [c.34]    [c.140]    [c.234]    [c.236]    [c.443]    [c.618]    [c.1099]    [c.112]    [c.272]    [c.256]    [c.208]    [c.183]   
Power supply cookbook (2001) -- [ c.234 , c.236 ]