Hysteresis losses

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. 

Eddy current and hysteresis losses are complex quantities and can be estimated in a laboratory, on no load, in the form of power input, le.ss and friction and windage losses etc. as shown in Section 11.5. Based... 

Figure 1.10 Hysteresis loop and magnetizing curve illustrating hysteresis loss...

Hysteresis losses, caused by cyclic magnetization of steel. 

Core loss is the magnetizing or hysteresis loss and represents the iron loss of the machine. 

The unbalanced voltage will produce an additional rotor current at nearly twice the supply frequency. For example, for a 2% slip, i.e. a slip of 1 Hz, the negative sequence stator current, due to an unbalanced supply voltage, will induce a rotor current at a frequency of (2/- 1) = 99 Hz for a 50 Hz system. These high-frequency currents will produce significant skin effects in the rotor bars and cause high eddy current and hysteresis losses (Section 1.6.2(A-iv)). Total rotor heat may be represented by... 

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... 

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

These balanced enclosure currents also induce electric fields into nearby structures, RCC beams and columns in the same way as the main conductors, and hence nullify most of the space magnetic fields. These space fields (fields outside the enclosure) are otherwise responsible for causing eddy current and hysteresis losses in the metallic (magnetic) structures, RCC beams and columns in the vicinity. The electrical bonding of enclosures thus... 

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. 

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. 

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... 

The designer can use several approaches to prevent hysteresis failure. The first is material selection. The stiffer the material is, the smaller the strain is for a given stress level and the lower the hysteresis loss per cycle. Some materials are additionally fairly linear in stress-strain characteristics and have smaller hysteresis loops. These would be preferred in dynamic loading applications. 

De Sarkar et al. [52] have reported a series of new TPEs from the blends of hydrogenated SBR and PE. These binary blends are prepared by melt mixing of the components in an internal mixer, such as Brabender Plasticorder. The tensile strength, elongation at break, modulus, set, and hysteresis loss of such TPEs are comparable to conventional rubbers and are excellent. At intermediate blend ratio, the set values show similarity to those typical of TPEs (Table 5.5). 

FIGURE 31.13 (a) Plot showing the stress-strain behavior of various irradiated rubbers, (b) Plot showing the variation of tensile strength and modulus of rubbers irradiated with different doses, (c) Plot showing the variation of hysteresis loss, set, and elongation at break of irradiated fluorocarbon rubbers. (From Banik, I. and Bhowmick, A.K., Radial. Phys. Chem., 54, 135, 1999. With permission.)... 

We shall deal in this lecture with recent improvements in the elastomers synthesis, that should be able to cope with the above mentioned requirements, without resorting to important investments for new plants or to cumbersome feedstocks. The improvement of the elastomer synthesis relies upon new catalytic systems that allow a control of elastomer tacticity in order to achieve a strain induced crystallization, and suitable monomer combinations in order to minimize the hysteresis loss of the elastomer in a wide range of temperatures and frequencies. 

An instrument designed to follow hysteresis losses in polymers by measuring the resistance to the rolling of small balls over the surface of the test piece it can investigate transitions in polymers to as low a temperature as -120 °C. Superseded by modem dynamic mechanical thermal analysis equipment. 

The close packing of the isobutylene chain confers on the polymer a high degree of impermeability to gases, but also results in a very lossy rubber. The high hysteresis loss can be utilised in some circumstances to provide good friction in wet conditions. 

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