54 



SCIENCE. 



[Vol. XIV. No. 338 



oped to the place where it is to be used, the form given to it for 

 economy of transportation may be changed so as to adapt it fully 

 to the uses for which it is intended. High tension may be ex- 

 changed for greater current, volts for amperes. This transforma- 

 tion is accomplished by the converter shown in Fig. 6. In this 

 converter, the core consists of a polygonal ring made of insulated 

 iron wire, so wound as to leave several concentric air-spaces in the 

 core. In the converters of the smaller sizes, the core is built up of 



FIG. 4.— BRUSH ALTERNAIIN'G .SYSTEM. 



■perforated thin iron plates (Fig. 7). In either case, the iron is so 

 divided that the efficiency of the converter is little less with half 

 ;than with full load. Upon each side of this core or iron ring is 

 wound a single layer of heavy copper wire. The four or five sin- 

 gle-layer coils carried by each half of the core are joined in series ; 

 and the two groups, borne by the two halves of the core, are joined 

 in multiple, the whole constituting the secondary coil. The termi- 

 .nals of this secondary coil connect with the secondary main line 

 running into houses and supplying current for the lamps. Most of 

 the converters are wound so as to give a secondary current of 



FIG. 7. — BRUSH ALTERNATING SYSTEM. 



about 100 volts, but may instantly be connected to give 50 volts 

 and twice as many amperes as before. They are made in sizes 

 that supply each from 5 to 250 i6-candle-power lamps, or more. 



Between the fine iron wire of the core and the heavy copper wire 

 of the superposed secondary coil, insulating pads one-eighth of an 

 inch thick are placed at the corners of the core. Between these 

 insulating corner-pieces are insulating air-spaces. Thus the cop- 

 per and the iron are separated from each other at the corners of 

 the core by their respective coverings and the insulating pads, and 

 at all other points by their respective coverings and open air- 

 spaces, the latter affording ample ventilation and facility of exami- 

 nation. 



Over each of these single-layer parts of the secondary coil are 

 bound a few layers of smaller copper wire to form a corresponding 

 part of the primary coil. These corresponding parts of the sec- 

 ondary and primary coils are separated from each other by insu- 

 lating pads at the corners and intervening air-spaces in the same 

 manner and with the same advantages as previously described. 



The ventilation of these converters is specially provided for, and 

 the insulation resistance is exceedingly high. It is impossible to so 

 overload the wire of the primary circuit as to force its current into 

 the secondary circuit : in other words, the high-tension current 

 cannot pass the converter. The converters are tested at the fac- 

 tory with double load, and, though no one has ever given out, over- 

 loading is made impossible by the use of safety-fuzes for the pri- 

 mary coils. These are extra long, and so mounted on slate or 

 porcelain strips that they may be removed or replaced with the 

 fingers merely, and without touching any metallic part of the con- 

 verter. 



The converter-coils, with safety-fuzes, etc., are placed in wind 

 and weather proof cast-iron boxes of pleasing design (Fig. 8), 

 and may be placed wherever most convenient ; the governing 



BRUSH ALTERNATING SYSTEM. 



principle being to do as much work as possible with the less ex- 

 pensive primary wire, and to shorten the more costly secondary 

 main. These converters are now made in sizes ranging from 

 2-lamp to 250-lamp capacity. With converters, as with dynamos, 

 the larger sizes are the most economical. With a loo-volt con- 

 verter fed by a 2,000-volt primary current, it is more easy and 

 profitable to run a short secondary main to supply several con- 

 sumers than to provide a converter for each consumer. 



Fig. 9 represents the ammeter, which is placed in the main or 

 feed circuit, wherever it is desirable to measure the strength of the 

 current. It is a compensated expansion device, acting on the prin- 

 ciple of one type of Brush arc lamp. It is free from any magnetic 

 action, the simple compensating arrangement insuring the normal 

 working of the apparatus at all temperatures. It is equally effi- 

 cient with direct and with alternating currents. 



The alternating-current apparatus of the Brush Electric Com- 

 pany here described is based on the patents of Charles F. Brush 

 and Gustav Pfannkuche, the latter having the supervision of this 

 branch of the Brush Electric Company's business. 



The heat in Russia and other parts of northern Europe has 

 been intense of late. The Central Observatory at St. Petersburg 

 has not recorded such a high temperature at the same time of the 

 year since 1774. 



