We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
CURRENT RECTIFICATION 303
If the available d. c. voltage is 220, then an installation will be justified because it is too costly to absorb all the wattage (represented by the amperage multiplied by the difference between the line (220) and arc voltages) through rheostatic resistance. If, for example, the amperage is 75, the line voltage 220 and the arc voltage 55, the waste would be 12,375 watts (220 — 55 = 165 X 75), or more than U1/^ kilowatts. But all other factors being normal, if the line voltage is only 110, then the waste would only be 4,125 watts (110 — 55 = 55 X 75), or 4% K.W., were rheostats used.
Remembering that motor generator sets, under average conditions, are only about 70 percent efficient (the general average is probably even lower), it is seen the difference in their favor is too small to justify their use where the power supply delivers 110 volts d. c.
(89) As a matter of fact motor generators, as a rule, possess an efficiency average of about 65 percent — that is, for every 100 watts taken from the power line, only 65 will be available at the light source. A well designed, well constructed set will have an efficiency of approximately 70 percent. But often because motor generators are seldom kept in perfect condition and adjustment, their actual efficiency drops until it is somewhere between 45 and 70. Very much depends upon the intelligent care given them by the man or men in charge.
(90) Both motor and generator should be mounted on one bed plate of metal and bolted solidly down. This insures a permanently perfect alignment of the motor and generator shaft — an essential quality since the shafts are rigidly connected, usually by means of a flanged, bolted, unyielding iron coupling.
(91) The generator may be either of the parallel type, which means a machine that maintains constant voltage under variations in current output, or it may be of the series type which, within the limits of its capacity, automatically increases or decreases its voltage as current flow (load) is raised or lowered. Generators employed in projection should be capable, while supplying one light source, of automatically increasing its voltage