This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1903 Excerpt: ...to force full load current through the transformer. For medium sized 2,000-volt lighting transformers the reactive pressure is usually between 3% and 6%. That is, with the secondary on short circuit, 60 to 120 volts applied to the primary will give full load current. The variable resistance shown in Fig. 29 is not necessary if about 100 volts are available. By measuring the current which this voltage produces, we may easily interpolate the voltage necessary to produce full load current. We now have the percentage pressure consumed by the resistance (this may be determined from the current and the equivalent resistance as explained), and by the impedance. The reactive pressure may be determined graphically as follows: Lay off the percentage resistance pressure, say 2%, horizontally, Fig. 30. From / draw a line, fg, of indefinite length, at right angles to bf. Then with b as centre, and a radius equal to the percentage pressure consumed by impedance, describe a circular arc to cut fg in g. The reactive pressure may be scaled off, or may be calculated by solving the right angle triangle. Having the percentage resistance and reactive pressure the regulation of the transformer on a lighting load may be determined by drawing a figure like 21, or for A inductive or capacity load by drawing a figure like 22. In determining the regulation of all fairly good transformers on any kind of a load the magnetizing current may be neglected. This is true because the magnetizing current is usually only about 2% of the full load current, and the addition of this to the load current only affects the ratio of transformation by a small fraction of a per cent. Besides, the magnetizing current is a constant and does not affect the regulation. The regulation of transformers that are...