Iron core

The term channel induction furnace is appHed to those in which the energy for the process is produced in a channel of molten metal that forms the secondary circuit of an iron core transformer. The primary circuit consists of a copper cod which also encircles the core. This arrangement is quite similar to that used in a utdity transformer. Metal is heated within the loop by the passage of electric current and circulates to the hearth above to overcome the thermal losses of the furnace and provide power to melt additional metal as it is added. Figure 9 illustrates the simplest configuration of a single-channel induction melting furnace. Multiple inductors are also used for appHcations where additional power is required or increased rehabdity is necessary for continuous operation (11). 

Note The embedded lemperalure deleclor melhod is inappropriate for stator windings, which have only one coil side per slot, in such ciises the resistance melhod must be used with the same limits of temperature rise. For checking the temperature of such a winding in service, an embedded detector at the bottom of the slot is of little use because it would give mainly the temperature of the iron core. A detector placed between the coil and the wedge will follow the temperature of the winding much more closely and is, therefore, better for check tests, although the temperature there may also be a little less than the actual one. 

Gapped iron core or saturated type reactors 27/849... 

For the theory of neutralization of the magnetic effect on the conductor in a non-magnetic shielding, refer to the continuous enclosures for isolated phase bus systems discussed in Section 31.2.2. As a result of non-magnetic shielding there will be no saturation of the iron core and the V-I characteristic of the reactor will remain almost linear. 

Unlike an air core, the inductor coil now has an iron core that may be provided with air gaps or non-magnetic... 

Similarly, gapped iron core reactors as shown in Figure 27.4, in which the iron core content is reduced by providing an air gap or non-magnetic material between the core laminations, also raise the saturation level (the core remaining unsaturated. Figure 27.1 I) to help provide an... 

Coreless, gapped iron core or / with magnetic shielding ... 

Unnecessary loading of the breakdown fuse through transient overvoltages can be avoided by connection to a r element which consists of a length choke and transverse capacitors. So-called iron core chokes are most conveniently used for series chokes, which are usual in power electronics. A damping element with a 61-fjF capacitor is advised at the input and output of the r element. 

The resistance method gives an average temperature of the whole winding. Some parts will be hotter than others usually the end turns will be somewhat cooler than parts of the winding in the middle of the iron core. NEMA committee members have been collecting test data on many machines to determine the correlation between temperature measurements by detector and by resistance, and the standards are periodically updated to reflect any of the technology improvements. 

American physicist Joseph Henry develops a coil magnet that grows stronger as more wire is wound around an iron core. He succeeds in lifting more than a ton of metal. Thermostat is invented. 

The inductance of an iron-cored inductor varies with any air gap included in the iron core. Thus, physical movement can be detected by allowing this movement to displace part of the core, so changing the width of the gap. The detection of very small movements is possible in this way, and instruments based on the principle are used to measure acceleration, pressure, strain, thickness and a variety of other changes. 

Rahmel and Tobolsk have shown that the iron core below triplex scales of Fe0/Fe304/Fe203 grown in Oj + water vapour at 950°C become enriched in H, indicating that water vapour can penetrate relatively thick wustite scales. Cracks are a valid path for such diffusion but penetration can occur even when the oxide can deform plastically and there is no evidence of cracking. ... 

The commonest form of level detector is a metallic float carrying an iron core which rises and falls within a sealing sleeve. An induction coil surrounds the sleeve and is used to detect the position of the... 

FIGURE 6.3 Sequence developing chamber by Buncak 1 — support with mobile phase source (reservoir), 2 — holding frame, 3 — magnet holder, 4 — magnet, 5 — cover plate, 6 — TLC plate, 7 — wick with iron core, 8 — solvent entry. (From Buncak, P., GIT Fachz. Lab. (Suppl., Chromatographie), G-I-T-Verlag, Darmstadt, 3-8, 1982. With permission.)... 

However, ferritins isolated from the bacterium Pseudomonos aeruginosa (Mann et ah, 1986) and from the chiton Acanthopleura hirtosa (St. Pierre et ah, 1990) have iron cores of limited crystallinity, despite having P Fe ratios of around 1 40, perhaps suggesting that core crystallinity is influenced by the rate of iron deposition as well as by the composition of the medium. The way in which phosphate may influence core development is discussed below. 

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