DOMESTIC EXPORTS-continued.

Electrical machinery and appliances, by country of destination, 1910-1921—Continued.

TELEGRAPH APPARATUS (INCLUDING WIRELESS).3

DOMESTIC EXPORTS-continued.

Electrical machinery and appliances, by country of destination, 1910-1921-Continued.

DOMESTIC EXPORTS-Continued.

Electrical machinery and appliances, by country of destination, 1910-1921—Continued.

This classification includes principally rotary machinery for generating electric currents, called generators; similar machines for utilizing electric power, called motors; and stationary apparatus for modifying certain characteristics of the current, called transformers. Essentially they are steel cores carrying insulated copper windings. Other types are control apparatus, switches, and other accessories. In 1914 domestic production of this class of machinery amounted to $95,000,000, and in 1919 to about $273,000,000.

Steel, including silicon steel, and copper, are the chief materials used. Many other materials that to a lesser extent also enter into the construction, include mica, treated paper and cotton, and other insulating materials.

Electrical machinery is made in machine shops by quantity production methods on a large scale. For the larger types of equipment large and expensive machines are necessary. The smaller parts are made on automatic machines, and the use of hand labor is confined chiefly to assembling and winding coils.

The output of two large firms predominates, although a great many of the smaller machines are made by smaller concerns. A well organized engineering staff is necessary, especially for the larger apparatus.

Pre-war exports averaged about $8,500,000 per annum. Owing largely to the removal of foreign competition during the war, exports greatly increased, and in 1921 amounted to more than $36,000,000. It is probable that export to Europe has been limited to some extent by international agreements among manufacturers.

Statistics of imports are not reported separately, but it is known that there is little importation. Foreign machines are a rarity in the United States.

Germany and England are the largest foreign producers; in each of those countries there are three or four large firms, similar to those of the United States, manufacturing a full line of machinery. Other producers of less importance are Belgium, Switzerland, Japan, and France.

The industry is well organized in the United States, and is carried on on a large scale by quantity production methods, which tend to keep costs at a low level. Material and labor cost average approximately 40 per cent each of the total cost of production; wages are lower in Europe, but the methods of production used in this country offset this to some extent, probably to a greater extent in the case of Great Britain than in the case of Germany.

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GENERAL INFORMATION.

Act of 1913, paragraph 167. Articles or wares not specially provided for in this section, if composed wholly or in chief value of iron, steel, lead, copper, brass, nickel, pewter, zinc, aluminum, or other metal, but not plated with gold or silver, and whether partly or wholly manufactured, 20 per centum ad valorem.

DESCRIPTION.

The apparatus treated in this survey is that used for the generation and utilization of electrical power currents, and the necessary ac

cessories.

In the class of rotary machines, generators and motors are the most important and widely used; there are also certain other machines used for modifying the various characteristics of the current. erators and motors are similar in construction; in fact, nearly all types may be used interchangeably, although in practice this is not done, as better results are obtained by certain minor differences in design. Both are made in all ranges of capacity, although of course generators average much the larger. The larger electric generators as now built are directly connected to steam turbines or water wheels, the two machines having a common shaft, and being known as a set. A generator or motor consists, essentially, of two iron or steel members, one of which is mounted on a shaft and revolves within the other and both of which carry copper conductors. The two members are often called the rotor and the stator. The series of conductors on one of these members is, in the case of a motor, connected to the power line or in the case of a generator is itself the source of supply. The series of conductors on the other member carries another current, which may be induced by the machine itself or may be supplied from an outside source. The action of the current sets up a magnetic flux through the iron, which, if power be supplied to rotate one of the members, generates the electric power current by its reaction on the conductors. Conversely, if the conductors are supplied with current from a power line, the machine will rotate as a motor.

Transformers form another large class of apparatus in which there are no moving parts whatever. They are used for increasing or decreasing the pressure of electric currents at the end of a transmission line. In order to avoid excessive losses on such a line, high pressures must be used, which can not be safely and conveniently applied to motors, lamps, or other apparatus. Transformers are

interposed in order to reduce the pressure for use in such apparatus. A transformer consists of a core built up of iron plates, around which are placed two windings of insulated copper wire. The passage of a current through one winding induces a current of a different pressure in the other winding, the ratio of the pressures in the two windings being determined by the ratio of the number of turns in the two coils.

The various types of control apparatus form another class, which are not machines, but usually have movable parts. Examples of this class are oil switches for opening and closing circuits, rheostats for limiting currents, lightning arresters, and various types of regulators.

The application of electric power is rapidly extending, and includes such important uses as the propulsion of locomotives and ships. Its wide use is due to the high efficiency of the electric motor, its convenience, and ease of control.

DOMESTIC PRODUCTION.

In 1914 the domestic production of the classes of electrical apparatus mentioned amounted to approximately $95,000,000. In 1919 production amounted to about $273,000,000, which was slightly over one-quarter of the total production of electrical material.

Materials-Steel and copper are the principal materials used in the construction of electric-power apparatus-copper on account of its electrical properties and steel for its magnetic characteristics. The greater part of the steel, which is used for carrying the magnetic flux, is of special quality, and is used in the form of stampings, which are built up to the required thickness. The use of laminations is necessary in order to avoid losses which would occur in solid metal. For other parts of machines, special steel rings are formed from rolled plate, or forced out of solid metal. Silicon steel is largely used for laminated parts of transformers and generators, as it combines desirable electrical and magnetic properties. Brass, Babbitt metal, solder, japan varnishes, and other materials are used in smaller amounts. Many varieties of insulating materials are required-cotton and paper treated with compounds for insulating the windings and mica for separating the copper bars of the commutator. Carbon is used in the form of small rectangular or round shapes, called "brushes," for conducting the current to the moving parts of the machine, and although the brushes are among the smallest parts of the machine, the character of the brush may greatly affect its operation. Carbon is treated in another survey of this series. The bulk of the materials are available from domestic sources, and the supply is ample. Mica is obtained from Canada, and small amounts of the varnishes used are imported.

Equipment. Works for the manufacture of electrical-power apparatus consist of foundries and forge and machine shops. Many of the smaller parts are made largely by automatic machines. The heavier apparatus, on the other hand, requires large and specially designed equipment for the accurate machining of heavy parts. Accurate work is necessary, as electrical machines are run at high speeds and carry heavy rotating members. Special machines and standard machines adapted to special uses are employed for such purposes as the winding of coils for machines and transformers.