Layers per portion

In Figure 3-9, we have also defined p, the layers per portion. Note how p gets reassigned when we interleave. 

Now let us apply what we have learned to our ongoing numerical example. We start by taking a copper foil wound twice on the ETD-34 bobbin — to form the 5 V secondary winding. Since this is interleaved with respect to the primary, only one turn belongs to each split section. So the layers per portion for the secondary is p = 1. We will calculate the losses, and if acceptable, we will stay with the resulting arrangement. 

If the losses are not acceptable, we may need to look for a bobbin that will allow a wider width of foil. Or we can consider paralleling several thinner foils to increase p. For example, if we take four paralleled (thinner) foils in parallel (each insulated from the others), we will get four effective layers for the secondary, and the layers per portion will then become 2. 

On the top left side of Figure 3-11, we have Dowell s original curves, which show how Fr varies with respect to X (i.e. h/S). The parameter for each curve is layers per portion (i.e. p). Note that Dowell s curves talk in terms of foils only. They don t care about the actual number of turns in the primary or secondary (i.e. from the electrical point of view), but only the effective layers per portion (from the field point of view). So, when we consider a layer of round wires of diameter d, we need to convert this into an equivalent foil. Looking back at the right side of Figure 3-8, we see that that this amounts to replacing a wire of diameter d with a foil slightly thinner (i.e. with the same amount of copper, but in a square shape). Alternatively, if we want to get a foil of X = 4 for example, we need to start with a wire of... 

However, the equivalent foil thickness is now half of what it was — 28 (i.e. X = 2). And we also now have two layers per portion from Dowell s standpoint. Consulting Dowell s curves, we get an Fr of about 5 now (marked B ). Since we are keeping Rdc fixed in the process, Rac oc Fr. Therefore now, decreasing Fr is a sure way to go, to decrease Rac- So an Fr of 5 is decidedly worse than an FR of 4. We now go ahead and subdivide once more, in a similar manner. So we then get four layers per portion, each with X = 1, and Fr has gone down to about 2.6 (points marked C ). We subdivide once more, and we get eight layers per portion, with X = 0.5. This gives us an Fr of about 1.5 (marked D ). This is an acceptable value for Fr. 

Note that by the process of subdivision, the number of layers per portion has gone up as... 

Interstitial fluid bathes the cells of the body and is protected from the external environment by the top layer of skin termed as the epidermis. The epidermis has an irregular thickness of 40-100 pm and is not vascularized, so viable cells receive nutrients by diffusion. The outer, dead, nonviable portion of the epidermis, termed as the stratum corneum, is 6-22 pm thick and about one-cell layer per day flakes off.19,20... 

Place 50 g. of anhydrous calcium chloride and 260 g. (323 ml.) of rectified spirit (95 per cent, ethyl alcohol) in a 1-litre narrow neck bottle, and cool the mixture to 8° or below by immersion in ice water. Introduce slowly 125 g. (155 ml.) of freshly distilled acetaldehyde, b.p. 20-22° (Section 111,65) down the sides of the bottle so that it forms a layer on the alcoholic solution. Close the bottle with a tightly fitting cork and shake vigorously for 3-4 minutes a considerable rise in temperature occurs so that the stopper must be held well down to prevent the volatilisation of the acetaldehyde. Allow the stoppered bottle to stand for 24-30 hours with intermittent shaking. (After 1-2 hours the mixture separates into two layers.) Separate the upper layer ca. 320 g.) and wash it three times with 80 ml. portions of water. Dry for several hours over 6 g. of anhydrous potassium carbonate and fractionate with an efficient column (compare Section 11,17). Collect the fraction, b.p. 101-104°, as pure acetal. The yield is 200 g. 

Immediately the reaction is complete, introduce through the condenser 250 ml. of 50 per cent, sulphuric acid (by weight) whilst cooling the mixture in ice and water and stirring vigorously. Transfer the mixture to a separatory funnel, remove the ether layer, and extract the aqueous layer with three 50 ml. portions of ether. Cool the combined ether extracts by the addition of ice, and add cautiously 100 ml. of 25 per cent, sodium hydroxide solution run off the aqueous layer and repeat the... 

Hydrolysis (or saponification) of n-butyl acetate. Boil 4-5 g. of n-butyl acetate (Section 111,95) with 50 ml. of 10 per cent, sodium hydroxide solution under reflux until the odour of the ester can no longer be detected (about 1 hour). Set the condenser for downward distiUation and coUect the first 10 ml. of distillate. Saturate it with potassium carbonate, aUow to stand for 5 minutes, and withdraw all the Uquid into a small pipette or dropper pipette. AUow the lower layer of carbonate solution to run slowly into a test-tube, and place the upper layer into a small test-tube or weighing bottle. Dry the alcohol with about one quarter of its buUr of anhydrous potassium carbonate. Remove the alcohol with a dropper pipette and divide it into two parts use one portion for the determination of the b.p. by the Siwoloboff method (Section 11,12) and convert the other portion into the 3 5-dinitrobenzoate (Section III, 27) and determine the m.p. 

Method 2 (from hydrazobenzene). Prepare a solution of sodium hypobromite by adding 10 g. (3-2 ml.) of bromine dropwise to a cold solution of 6-0 g. of sodium hydroxide in 75 ml. of water immersed in an ice bath. Dissolve 9-5 g. of hydrazobenzene (Section IV,87) in 60 ml. of ether contained in a separatory funnel, and add the cold sodimn hypobromite solution in small portions. Shake for 10 minutes, preferably mechanically. Separate the ether layer, pour it into a 100 ml. distilling flask, and distil off the ether by warming gently on a water bath. Dissolve the warm liquid residue in about 30 ml. of alcohol, transfer to a small beaker, heat to boiling on a water bath, add water dropwise to the hot solution until the azobenzene just commences to separate, render the solution clear again with a few drops of alcohol, and cool in ice water. Filter the orange crystals at the pump, and wash with a little 50 per cent, alcohol. Dry in the air. The yield is 8 g. 

Concentrate the mother liquors from this recrystallisation and combine with the oily filtrate dissolve in 250 ml. of 10 per cent, sodium hydroxide solution, and extract with two 50 ml. portions of ether to remove non-phenolic products. Acidify the alkaline solution with hydrochloric acid, separate the oily layer, dry it over anhydrous magnesium sulphate, and distil under diminished pressure, preferably from a Claisen flask with fractionating side arm (Figs. II, 24, 2-5). Collect the o-propiophenol (65 g.) at 110-115°/6 mm. and a further quantity (20 g.) of crude p-propiophenol at 140-150°/ 1 mm. 

In a 500 ml. flask, fitted with a reflux condenser, place 53 g. of 1-chloro-methylnaphthalene (Section IV.23), 84 g, of hexamethylenetetramine and 250 ml. of 1 1 acetic acid [CAUTION 1-Chloromethylnaphtha-lene and, to a lesser degree, a-naphthaldehyde have lachrymatory and vesicant properties adequate precautions should therefore be taken to avoid contact with these substances.] Heat the mixture under reflux for 2 hours it becomes homogeneous after about 15 minutes and then an oil commences to separate. Add 100 ml. of concentrated hydrochloric acid and reflux for a further 15 minutes this will hydrolyse any SchifiF s bases which may be formed from amine and aldehyde present and will also convert any amines into the ether-insoluble hydrochlorides. Cool, and extract the mixture with 150 ml. of ether. Wash the ether layer with three 50 ml. portions of water, then cautiously with 50 ml. of 10 per cent, sodium carbonate solution, followed by 50 ml. of water. Dry the ethereal solution with anhydrous magnesium sulphate, remove the ether by distillation on a steam bath, and distil the residue under reduced pressure. Collect the a-naphthaldehyde at 160-162718 mm. the yield is 38 g. 

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