AC Types

Almost all modem electric power for homes and factories is ac, mostly because its voltage can easily be stepped up by transformers, sent long distances with very little power loss, and then stepped down to 120V or 208V, etc., nearer to the user. The reason for such small power loss is that the heat loss is mainly 

The use of ac has an advantage in that no commutator is needed. The ac magnetic field of the coil (almost always with an iron core) will induce an ac current in any nearby conductor, so a copper or aluminum bar can be the rotor, as in Fig. 20.2. 

Very small motors such as this are often used in electric power meters, which the electricity supplier installs in a house or business to determine how much money to charge the user each month. This motor is not powerful, and it needs something else to get it started, which is not shown in the diagram. 

Once it gets going, the rotor has to come around to the correct position for repulsion, just in time for the next ac cycle to occur. This is one of the principles of ac induction motors, and the speeds are usually synchronous with the 60 Hz ac. That is, the revolutions per minute (rpm) is 60 times per minute, divided by some factor that is dictated by the design, although there is a few percent of slippage behind an exactly synchronous speed. (Experiments with controlling the speed of an ac motor will be described in the next chapter.) 

There are advantages to using an electrically conductive coil for the rotor, as shown in Fig. 20.3, This can provide much higher starting torque, because of the multiple turns in the winding. 

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Specifications and Standards, Shipping. Commercial iodine has a minimum purity of 99.8%. The Committee of Analytical reagents of the American Chemical Society (67) and the U.S. Pharmacopoeia XXII (68) specify an iodine content not less than 99.8%, a maximum nonvolatile residue of 0.01%, and chlorine—bromine (expressed as chlorine) of 0.005% (ACS) and 0.028% (USP), respectively. In the past these requirements were attained basicaHy only by sublimation, but with processing changes these specifications can be met by direct production of iodine. Previously the impurities of the Chilean product were chiefly water, sulfuric acid, and insoluble materials. Improvements in the production process, and especiaHy in the refining step, aHow the direct obtainment of ACS-type iodine. Also, because of its origin and production process, the Chilean iodine has a chlorine—bromine impurity level of no more than 0.002%. 

In the last decade, several new synthetic routes have been developed to allow the synthesis of various stable acyclic disilenes including ( )- and (Z)-ABSi = Si AC-type disilenes, but disilenes with the types of A2Si = SiBC and ABSi = SiCD are still unknown. 

Assign AC-type generics (if needed) reflecting connectivity aspects. 

The alteration of product structures by domain repositioning. The terminal thioesterase domain of surfactin synthetase has been repositioned to obtain acyl-tetra- and pentapeptide fragments in vivo of the cycloheptapeptidolactone [104], In the case of ACV synthetase, repositioning of the thioesterase domain would be expected to lead to dipeptides of the AC type. If this specific thioesterase would only release peptides of the D-configuration, alternative thioesterases from other NRPS systems might work. 

As commented in I rcface, the self-healing behavior of every self-healing liquid chemical, with the exception of liquid high explosives, such as nitroglycerin, of the true AC type, is ofthc TD type, so tltat a sclf-hcating liquid chemical of the TD type or self-heating liquid chemicals of the TD type are described hereafter simply as a liquid or liquids. 

Since the 1980 s, people called the chemicals safety circles appeared and attempted to calculate the so-called SADT for each individual self-heating chemical. They, however, attempted to do so by applying a few equations, which appear in the initial stages of the derivation process of the Semenov equation, to every self-heating chemical, irrespective of whether it is of the TD type or of the AC type, or, irrespective of whether it is liquid or solid. We have, therefore, no choice but to say that, theoretically speaking, their approach to the subject was almost meaningless. 

A broad classification of self-heating chemicals into the two large groups, f.e., the TD type and the AC type... 

As stated in Preface, each individual self-heating chemical, including every gas-permeable oxidatively-heating substance, is classified into either of the two large groups, i.e., the thermal decomposition or TD type and the autocatalytic reaction or AC type. 

Figure 5. The whole self-heating process up to the thermal explosion of 2 cm of a chemical of the I D type charged in the open-cup cell, or confined in the closed cell, in accordance with the self-healing property of the chemical, and subjected to the adiabatic self-heating lest started from a 7j, and, the whole sclf-hcating process up to the thermal explosion of 2 cm of a high explosive of the true AC type confined in the closed cell and subjected to the adiabatic self-healing test started from a Tj on the low temperature side.

It is well-known that such a self-heating behavior as described above is observed really in the spontaneous ignition process of a nitrate ester, such as collodion cotton (Fig. 6). Chemicals of the true AC type thus form a group intrinsically different, in the decomposition reaction mechanism, from chemicals of the TD type. 

As will be explained hereafter in the present chapter, the self-heating behavior of a powdery chemical of the quasi-AC type is also of the AC type. 

Derivation of an empirical formula, nAt = alT, + b, Le., Eq. (59), which is used to calculate the SADT for a chemical of the AC type, including every powdery chemical of the quasi-AC type, having an arbitrary shape and an arbitrary size, confined in an arbitrary closed container of the corresponding shape and size, and placed in the atmosphere under isothermal conditions... 

As a matter of fact, however, Eq. (56) is reduced to the following form, because the effect of the concentration of a high explosive of the true AC type on the rate of the decomposition reaction of the high explosive to generate the autocatalyst in the induction period is assumed to be of the zeroth order. 

In fact, when confined in the closed cell and subjected to the isothermal storage test performed at a T, 2 cm of a high explosive of the true AC type warms up to the T, within tens of minutes, but the temperature remains at the T,... 

The SADT for a high explosive of the true AC type depends on the induction period of the autocatalytic reaction however, the autocatalytic reaction does not depend, in principle, on the quantity of the high explosive. On the other hand, as will be explained hereafter in the present chapter, the SADT for a powdery chemical of the quasi-AC type depends on the phase transition, the melting however, it does also not depend, in principle, on the quantity of the chemical. 

In addition to chemicals of the TD type and those of the true AC type, there exist chemicals refeired to as powdery chemicals of the quasi-AC type. 

Correlation among the pattern of the TG-DTA curve of a self-heating powdery chemical, the two types of self-heating behaviors, Le., the TD type and the quasi-AC type, and the two equations of the thermal explosion theory... 

The type of the self-healing behavior of a self-healing powdery chemical is closely related to the pattern of the thermogravimctry-diffcrcntial thermal analysis (TG-DTA) curve which the chemical affords. In other words, it is possible, in principle, to infer the self-healing behavior of a self-healing powdery chemical to be either of the TD type or of the quasi-AC type by glancing over the TG-DTA cuiwe of the chemical, so that it is also possible to infer the equation of the thermal explosion theory applied to calculate the of the chemical to be either the Semenov equation, i.e., Eq. (17) presented in Section 1.2, or the F-K equation, i.e., Eq. (29) presented in Section 1.3, or neither equation. 

On the other hand, individual TG-DTA cuiwcs, which are also each recorded with the glass open-cup cell, 5 mm in diameter, 2.5 mm in depth, at the same value of 0 of 2.5 K/min in air at atmospheric pressure, of four of the live powdery chemicals of the quasi-AC type, which are listed in Table 26 in Subsection 10.4.1, are presented in Fig. 9. 

Figure 9. Individual TG-D l A curves of the four powdery ehennleals of the quasi-AC type.

It is obvious in Fig. 9 that one characteristic of the DTA curve of a powdery chemical of the quasi-AC type is the presence of the melting point [22]. Another characteristic of the DTA curve of a powdery chemical of this type is that the curve shifts successively from the endothermic peak caused by melting... 

The property of each individual powdery chemical of the quasi-AC type varies in a continuous fashion with the interval between the cndothcnnic peak and the exothermic peak in the DTA curve which the chemical affords. Both peaks arc in particular close together in the case of ABCN or AMVN, as shown in Fig. 9. The pattern of the DTA curve of a typical powdery chemical of the quasi-AC type, such as ABCN or AMVN, is thought to reflect the fact that, when heated, a phase transition, the endothermic melting, takes place in parallel with a chemical reaction, the exothermic decomposition reaction, in it, as shown diagrammatically in Fig. 10. 

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