The current produced by an electric generator is of relatively low pressure, and for that reason it is impracticable to utilize it, for power purposes, more than 5 or 6 miles from the central station. It was found, however, that this pressure, or voltage, could be increased by the use of a transformer or converter, consisting of a metal core, through and around which are wound primary insulated wires leading from the generator. Secondary wires, also insulated, are wound through and around the same core, and carried thence to the point of application. The voltage is increased or decreased according as the secondary wires are wrapped around the core more or less frequently than the primary wires.
One of the consequences of thus transforming the current is the generation of heat. In small machines this is corrected by radiation, but in large ones the heat 'ages' the iron, lessens the efficiency of the transformer, and, in time, deteriorates the insulation around the wires. This latter result causes short circuits, makes it impracticable to take advantage of the increased voltage, and thus again restricts the area in which currents of more than 10 K. W. can be used for producing light and power. 112 Fed. 418.
Many efforts were made to overcome this difficulty, but without success until July 12, 1887, when George Westinghouse, Jr., secured patent 366,362 for an 'Electrical Converter,' which, his application stated, was intended to prevent the converter becoming 'overheated when employed for a long time in transforming currents of high electro motive force.' Extracts from the specification and claims are copied in the margin.
The core is preferably composed of thin plates of soft iron . . . separated individually or in pairs from each other by thin sheets of paper or other insulating material. . . . The plates are preferably constructed with two rectangular openings through which the wires pass. . . . Each group of-say five or six plates-is preferably separated from the succeeding group by air spaces. These may be produced by passing tubes, which may be of soft iron or other metal, or of vulcanized fiber, along the lengths of the plates. It may be sufficient in other cases to block the group of plates apart at intervals instead of extending the tubes the entire lenght. Preferably also the primary and secondary coils are separated from each other in a similar manner.'
Where the converter is to be used in the open air, the tube will permit a free circulation of air and thus aid in keeping the converter cool.
It may be preferred in some instances to surround the converter with some oil, or paraffin or other suitable material, which will assist in preserving insulating and will not be injured by heating. This material, when in a liquid form, circulates through the tubes and intervening spaces of the coils and plates, and preserves the insulation, excludes the moisture, and cools the converter.
The entire converter may be sealed into an inclosing case . . . which may or may not contain a nonconducting fluid or gas.
'I claim as my invention . . . 1 . . .; 2 . . .; 3 . . .