CHAPTER TWO
Edison, Westinghouse, and Electric Power
Electric power is indispensable to modern life. Telephones, lights, elevators, and computers depend on electricity, as do the ignition systems of cars and airplanes; without it, society would not have advanced beyond the nineteenth century. Thomas Edison is best known for having invented a new kind of light bulb, but his bulb was not an isolated invention. It was part of a network that Edison engineered to produce and distribute electric power from central generating stations. Following the success of his first power and light network, Edison created generating plants and distribution lines to bring electricity to homes and workplaces that found a wide range of uses in addition to indoor illumination.
Edison used a form of electricity known as direct current, which was practical in places, such as cities, where the users of power were close to the generating plant. Direct current could not be transmitted economically over distances longer than one or two miles. Within a few years, engineers found that a different form of electricity, alternating current, was more practical for longer-distance transmission. Edison could not bring himself to abandon his original technology and embrace alternating current, and a rival entrepreneur, George Westinghouse, seized the opportunity to supply alternating current to users of electric power in competition with Edison. Alternating current has since become the standard for transmission to households and workplaces.
Electricity and Light
Before the nineteenth century Americans relied mainly on candles for light. In 1816 the first U.S. company to provide street lighting with coal gas began operations in Baltimore, processing gas from burning coal and piping it to streetlights. Gas was also piped into urban homes and offices to light indoor lamps. A new petroleum-refining industry arose in the 1850s to supply customers beyond the reach of urban gas networks with kerosene to light indoor lamps (see chapter 4). Indoor gaslight and kerosene were fire hazards, though, and kerosene also produced smoke.1 The use of electricity for light attracted interest as an alternative.
During the eighteenth and early nineteenth centuries, scientists had learned new principles of electricity and magnetism. In 1800 Alessandro Volta of Italy showed that an electric current flowed around a closed wire circuit connected to a battery (sidebar 2.1). An electrical pressure, later named voltage, caused the current to flow. Hans Christian Ørsted of Denmark and André-Marie Ampère of France discovered that an electric current flowing through a wire circuit generated a magnetic field around itself. Ampère also found that coiling the wire created a stronger magnetic field inside the coil and made it an electromagnet. In 1825 William Sturgeon of England created a stronger electromagnet by passing current through a wire coiled around a U-shaped iron bar. Georg Ohm in Germany studied the resistance of circuits to the flow of current. He discovered a relationship, now known as Ohm’s Law, V = IR, which stated that voltage (V) is equal to current (I) times resistance (R).2
Experiments in the early nineteenth century showed that electricity could be employed to produce light. In 1808 Sir Humphry Davy in England demonstrated an arc light by connecting two carbon rods to a battery. When he touched the rod tips to each other and then separated them, electricity jumped between the tips in a brilliant arc. In the 1840s Sir William Grove ran an electric current through a platinum wire, heating the metal and causing it to incandesce or emit light. Neither arc nor electric incandescent light was practical, though, as long as the only sources of electricity were batteries, which could supply electric power only in small amounts.3
In 1831 Michael Faraday of England discovered that rotating an armature in a magnetic field induced a voltage, causing a current to flow in a closed circuit attached to the armature (sidebar 2.2). As long as there was an external source of mechanical power to rotate the armature, the method could generate electric current continuously. This current became known as alternating current (A.C.), because with each half revolution of the armature, the voltage reversed direction. Engineers soon invented an attachment (the commutator) that allowed only current in one direction to flow from the armature into the circuit. Current flowing in a single direction became known as direct current (D.C.). Feeding back some current to a coil around the magnet, making it an electromagnet, strengthened the magnetic field. Machines that produced electric current became known as generators or dynamos, and engineers soon found uses for the electricity that they could supply.4
The Electric Circuit
Electromagnetism
Magnetism to Electricity
Direct and Alternating Current
In 1870 the Belgian Zénobe Théophile Gramme invented a practical dynamo producing direct current with a steam engine to rotate the armature, which the Russian inventor Paul Jablochkoff used in 1878 to power arc lights in Paris, France. The following year Charles F. Brush began to operate systems of arc streetlights in American cities using steam engines and dynamos to produce direct current. Arc lights were far brighter than gaslights and soon became popular for lighting streets. But arc lights were not practical for lighting homes and offices because they were too intense.5 Thomas Edison believed that the key to indoor illumination was to use incandescent electric light supplied from generators, and he resolved to develop a system of incandescent light and power.
Edison and Incandescent Light
Thomas Alva Edison (1847–1931) learned telegraphy at age fifteen. After working as an itinerant telegraph operator, a growing passion for invention drew him to Boston and then to New York, where he improved the telegraph printers used to transmit gold and stock prices. With money from this work, he launched a business in Newark, New Jersey, making telegraph equipment. In 1876 Edison established a laboratory in Menlo Park, New Jersey, where with a team of assistants he devoted himself to research (figures 2.1 and 2.2). In 1877, Edison invented the phonograph that made him internationally famous. But his greatest achievement was to develop a system to provide incandescent electric light.6
Arc lights were connected to each other in series; a single circuit connected the lights and turned them on and off at the same time.7 However, incandescent indoor lighting would be practical only if each lamp could be turned on and off individually, at different times. To make lights operate in this way, Edison designed a parallel circuit in which, when some lamps were turned off, current would still flow to other lamps that were turned on (sidebar 2.3).
Some influential scientists and engineers argued that such a network could never work. Lamps needed electric power (P) to operate, and in 1840 the English scientist James Joule had defined electric power as the voltage times the current, a formula that came to be known as Joule’s Law, P = VI. Experts in the 1870s assumed that the power available to each lamp on a parallel circuit would diminish by the cube of the number of lamps (see appendix). But Edison realized that a dynamo could supply more lamps by simply generating more power. In the parallel circuit design, voltage had to be constant, so that the voltage supplied was the same to each lamp, whether one light or all of the lights were turned on. Edison designed his system to meet the demand for power at a standard voltage by varying the total current.8
Figure 2.1. Thomas Alva Edison in 1881. Source: “Edisonia”: A Brief History of the Early Edison Electric Lighting System (New York: Association of Edison Illuminating Companies, 1904), p. 78.
Figure 2.2. Menlo Park laboratory interior, 1880. Courtesy of Edison National Historic Site, West Orange, NJ. Neg. No. 6924.
The problem facing Edison was the relation of current to resistance expressed in Ohm’s Law, V = IR. By substituting IR for V, Joule’s Law can be rewritten as P = I2R. In a network of incandescent lamps, resistance (R) would consist of two components: the resistance of the filament (the thin material in the lamp bulb that emitted light when heated) and the resistance in the generator and the transmission lines. The power needed to supply a network of lamps would equal the sum of two numbers: the current I2 multiplied by the filament resistance, and the current I2 multiplied again by the resistance in the generator and the lines. To deliver power to the lamps, one alternative was to use a relatively high current with a low resistance in the lamp filaments. But such a low resistance would have raised the cost of transmission. The resistance in a transmission line was the product of the resistivity of the conducting material (a fixed value, ρ) and the line length (L), divided by the cross-sectional area (A) of the line (sidebar 2.4). A low resistance in the line would have required a line with a large cross-sectional area, and the best conducting material, copper, was expensive.
Edison’s great insight was to see that if he could instead raise the resistance of the lamp filament, he could reduce the amount of current needed to deliver a given amount of power. The cross-sectional area of the transmission lines could then be much smaller. In his preliminary calculations, Edison estimated that his lighting system could compete with indoor gaslights if it delivered electric power to incandescent bulbs with 100 volts, a current of 1 amp, and a filament resistance of about 100 ohms.9 (The actual system he built would operate on 110 volts, 0.75 amps, and 147 ohms per bulb.) Arc lights typically operated on a current of 10 amps and their carbon rods had a resistance of about 5 ohms.10 To be economical, Edison’s system required a low current, which in turn depended on finding a lamp filament with high resistance.
Series Circuits for Arc Lamps
Parallel Circuits for Incandescent Lamps
Ohm’s Law and Resistance
Upton’s Calculations
Filaments tested by earlier inventors burned out quickly and Edison at first tried to find a longer-lasting metal. In September 1878 he announced that he would soon have a system of incandescent light on the assumption that platinum would be a durable filament. The following year, though, he found that heated platinum released trace gases that caused the filament to burn out too quickly for practical use. Edison eventually decided that a carbonized thread would work as a high resistance filament in a bulb with a high vacuum. A device to create such a vacuum, the mercury pump, had been invented in the mid-1860s, and Edison improved it for his own use. Over the night of October 21–22, 1879, he and his staff tested a vacuum bulb containing a carbon filament with a resistance of more than 100 ohms. The bulb gave the desired illumination (16 candlepower) for 14A hours on 1 amp of current (figure 2.3). Edison filed a patent for the bulb on November 1, 1879.11
In developing his bulb, Edison differed from the approach taken by Sir Joseph Swan (1828–1914), an English chemist who had taken an interest in incandescent light as early as 1848. Swan resumed his light research in 1877, and in early 1879 he demonstrated an incandescent bulb. But Swan designed his bulb to have a low resistance, and he did not develop a practical filament until 1880. His approach was to demonstrate the bulb as an isolated laboratory experiment; the needs of a commercial system played no role in his thinking. To avoid protracted litigation, though, Edison reached an agreement with Swan in 1882 to share the British market.12
The parallel circuit and the high-resistance filament were crucial to Edison’s system, but he needed to solve two further problems before he was ready to build it. One was related to distance. A constant voltage would eventually diminish the farther it went from the generator. To offset the line loss associated with increasing distance, Edison would have needed to increase the cross-sectional area of his transmission lines, increasing their cost. Instead, he designed shorter feeder lines to go out from the power plant. Over these lines voltage would fall from 120 to 110 volts. The feeders would connect to service mains and lamp circuits that could operate on 110 volts. Besides distributing power more efficiently, the system of feeders and mains reduced to one-fifth the amount of copper that Edison believed his lines would otherwise require.13
Figure 2.3. Replica of 1879 Edison light bulb. Courtesy of General Electric Archives, now the GE Photograph Collection, Schenectady Museum, Schenectady, NY.
Finally, Edison needed a more efficient dynamo to generate electric power. Scientists and engineers in the 1870s assumed that the internal resistance in a dynamo had to be in balance with the external resistance of the circuit and the lamps on it, because a battery achieved the most efficient output of power when internal and external resistances were equal. But with a dynamo, balancing the resistances meant losing half of the energy in the generator itself. In contrast to his lamps, Edison realized that he would need to have a dynamo with very low internal resistance (sidebar 2.5). No existing generator could meet this need, so while they worked on the other elements of their system, Edison and his team designed a new dynamo with a low internal resistance that generated direct current with an efficiency of more than 90 percent (figure 2.4).14
As the location of his first network, Edison chose the center of American finance, the Wall Street district of New York City. He calculated that 10,000 gaslights in the district cost $136,875 to operate four hours per day. Edison believed that he could supply a similar number of incandescent electric lamps giving the same luminosity for $90,886 per year, with a start-up cost of $150,680. The cost of launching his system proved to be twice this amount, but the success of his bulb in 1879 enabled Edison to raise the money from investors led by the banker J. P. Morgan. On September 4, 1882, the network began operation from a central generating plant on Pearl Street, where six steam engines turned six “Jumbo” dynamos, so named by Edison for the elephant featured in the P. T. Barnum traveling circus. Each dynamo supplied power to about 1,200 lamps, and each lamp received 110 volts and 0.75 amps and had a filament resistance of about 147 ohms. Electric power is now measured in watts, and each lamp used 82.5 watts (110 volts times 0.75 amps). To measure usage, Edison developed an electrochemical meter and then charged by the kilowatt-hour (1,000 watts per hour).15
Edison soon launched companies in other states and countries to make power equipment, manufacture light bulbs, and provide electric utility service. His American firms merged in 1889–90 to form the Edison General Electric Company.16 In addition to supplying lamps, direct current from generators made electric motors practical. These worked as generators in reverse: direct current supplied to an armature inside a magnetic field caused the armature to rotate, producing mechanical power. Electricity provided industry with a new way to drive machines.17
Westinghouse and Alternating Current
Thomas Edison’s system worked well in urban and industrial areas where power plants could be located close to consumers. But Edison’s network could not extend over longer distances because voltage (and thus power) losses increased with the length of transmission lines. To prevent the dimming of lights with distance, Edison devised ways to branch and wire his system more efficiently. But he found that he could not transmit power economically over a distance of more than about two miles.18
Figure 2.4. Pearl Street station dynamo room. Source: Scientific American, 47:9 (August 26, 1882): 127.
George Westinghouse (1846–1914) found a way to transmit electric power over longer distances by switching from direct to alternating current. Born near Schenectady, New York, Westinghouse worked in his father’s machine shop and invented a device for putting derailed train cars back on track. After moving to Pittsburgh in 1868, he studied the problem of braking locomotives, a growing hazard as hand-turned brakes became more difficult to operate on heavier trains. In 1869 Westinghouse invented the compressed air brake and formed a new company to sell air brakes to the Pennsylvania Railroad and other rail lines. This invention made him wealthy (figure 2.5).19
Figure 2.5. George Westinghouse. Source: Francis E. Leupp, George Westinghouse: His Life and Achievements (Boston: Little, Brown, 1918), frontispiece.
Westinghouse also discovered natural gas under his Pittsburgh estate that was under high pressure. The gas had commercial value but only if the pressure could be reduced for delivery to consumers. Westinghouse devised a system that sent the high-pressure gas long distances through relatively inexpensive small-diameter pipes. At customer locations, he switched to large-diameter pipes, transforming the flow from high pressure to low pressure. This idea of high-pressure transmission and low-pressure usage helped him see the value in a new mode of electrical power supply, when he read an article in 1885 about an English system that used alternating current to supply power to incandescent lamps.20 The key to the new system was the use of transformers.
A transformer (sidebar 2.6) can be thought of as a ring-shaped core of magnetizable material, usually iron or steel, with two separate wire circuits, one coiled around each side of the ring core. Engineers call the first wire the primary circuit and the other the secondary, and normally each circuit is closed. With power equal to voltage times current, P = VI, we can designate the power in the primary circuit V1I1 and the power in the secondary circuit V2I2. Using alternating current for I, V1I1 induces a magnetic flux in the ring core. The change in flux induces a voltage V2 and causes a current I2 to flow in the secondary circuit.
Direct current is not practical to use in a transformer because current going in one direction induces a steady (and only momentary) flux in the ring core. However, an alternating current induces a flux change in the ring core each time it changes direction. The continuous changes enable an alternating current to sustain itself in a closed secondary circuit. A transformer can also reduce or increase the voltage between the two circuits according to the ratio of turns that the two wires make around the ring. As shown in sidebar 2.6, the ratio of primary to secondary turns is one to twenty. If we assume no power losses in the transformer, 50 volts and 800 amps in the primary circuit will transform into 1,000 volts and 40 amps in the secondary. A transformer can in this way step up the voltage and step down the current for long-distance transmission, so that line losses (proportional to I2 in the line loss P = I2R) can be kept low. A transformer at the other end can then step the voltage back down and the current back up for domestic and industrial use.21
Westinghouse realized that he could transmit electric power over much longer distances than Edison by using alternating current and transformers. After studying some transformers that he ordered from England in late 1885, he paid William Stanley, an electrical engineer in Great Barrington, Massachusetts, to develop a better transformer. In January 1886 he formed the Westinghouse Electric Company and tested Stanley’s transformers the following autumn with incandescent bulbs that Westinghouse designed. An alternating current generator produced 800 amps at 50 volts that stepped up to 1,000 volts and 40 amps for transmission from Pittsburgh to the town of Laurenceville, four miles away. Transformers there stepped the voltage back down and distributed it to 400 lamps, giving each lamp 50 volts and 2 amps.22
Edison’s bulbs did not operate with the same volts and amps, but the difference in efficiency can be seen by comparison: to power 400 of Edison’s bulbs, at 110 volts, an Edison line would have had to carry a current of 300 amps. Unable to use transformers, the Edison line would have needed more than fifty-six times as much copper wire as the Westinghouse line to transmit this current over the same four miles with the same line loss. If Westinghouse had stepped up his transmission voltage to 10,000 volts instead of 1,000, his alternating current could have traveled 400 miles with the same line loss.
Westinghouse soon received orders for A.C. generating systems. By the end of 1890, he had sold 350 central station alternating-current systems to challenge the Edison General Electric Company’s 400 direct-current central stations.23 Edison bitterly fought alternating current in the 1880s, in what became known as the “Battle of the Currents,” in part because he was unwilling to abandon the system that had earned him success and in part because he believed that alternating current was dangerous. Edison tried to persuade state legislatures to limit transmission to several hundred volts, which would have deprived alternating current of its economy, and to discredit A.C. further by emphasizing its risks, he supported its use to execute criminals.24 But
Westinghouse showed that the alternating current could be safe for local use, and he seized the opportunity that Edison gave him to create a new market, especially in areas where direct current was not economical. Light bulbs could work on alternating current, because at sixty cycles per second the flicker was too rapid to be noticed by the human eye.
The Edison company needed to offer A.C. equipment to remain competitive, and in 1892, Edison General Electric merged with a rival firm, Thomson-Houston, which had alternating-current technology. The merger created the General Electric Company (GE).25 Edison left the business and moved on to other interests, such as motion pictures, while Westinghouse continued to manage his own company. Westinghouse scored a public relations triumph by illuminating the 1893 Columbian Exposition in Chicago. GE and Westinghouse reached a patent-sharing agreement in 1896 and thereafter dominated the manufacturing of electrical equipment in the United States.26
Incandescent light did not cause gas and arc light to die out at once, and kerosene lamps continued to be needed in remote areas until rural electrification arrived. But gas, arc, and oil light eventually declined in the twentieth century. The gas companies found a new market supplying piped gas to kitchen cooking ranges and home heaters.27 Electric utilities eventually became separate publicly regulated companies, leaving GE and Westinghouse to manufacture electrical goods. As the twentieth century advanced, electricity became an increasingly vital part of modern life.28
Engineering Research and Practice
As the electrical industry matured, it began to rely on engineers with more formal training in mathematics and science. With alternating current, a number of complex technical challenges had to be overcome for the technology to be used more efficiently and more widely. A key problem was the lack of an electric motor able to work on alternating current. In a D.C. motor, supplying direct current to an armature inside a static magnetic field caused the armature to rotate. Alternating current, however, produced no rotation. The armature tried to rotate in alternate directions, causing each motion in one direction to be canceled by the motion in the other.
Nikola Tesla (1856–1943) invented a motor that solved this problem by rotating the magnetic field. Tesla had studied engineering in Austria and had emigrated from his native Serbia to the United States in 1884 (figure 2.6a). Three years later, he patented an electric motor in which an armature stood at the center of four coils arranged in a ring at ninety-degree angles to each other. An alternating current went to one opposite pair of coils. When the current reached its maximum, a second alternating current went to the other opposite pair. The currents pulled the armature magnetically and caused it to rotate. In addition to working on alternating current, the motor did not require metal contacts between the circuits and the armature and thus avoided the sparking that occurred with such contacts in direct-current motors. Tesla patented other inventions but sold his patents early in his career. He failed as an entrepreneur and died in tragic obscurity.29
A second problem was magnetic loss in transformers. Charles Steinmetz (1865–1923) solved this difficulty and went on to set new standards in the design of alternating-current technology as an engineer for General Electric (figure 2.6b). Born in Germany, he nearly completed a doctorate in mathematics when he had to flee the country in 1888 because of his socialist views. After engineering study in Zurich, Switzerland, he arrived in New York City and found work in a small firm that made electrical equipment. He soon turned his attention to the problem of magnetic loss. Just as electric current had to overcome resistance in a circuit, so did the magnetic flux have to overcome a resistance (called reluctance) in a metal transformer. In 1890 Steinmetz devised a formula to measure this loss so that engineers could design transformers to work more efficiently.30 General Electric acquired his employer in 1893, and the following year Steinmetz moved to the main GE plant in Schenectady, New York, to head its calculating department. Here he developed an approach to the design of alternating-current circuits that provided engineers with a practical way to understand them.31
Figure 2.6a. Nikola Tesla. Courtesy of the Prints and Photographs Division, Library of Congress, Washington, DC. LC-USZ62-61761.
Figure 2.6b. Charles Steinmetz. Courtesy of General Electric Archives, now the GE Photograph Collection, Schenectady Museum, Schenectady, NY.
Steinmetz made his contributions at a time when engineering was beginning to develop a more professional identity. In the late nineteenth century, universities began to establish new engineering departments, and engineers began to organize professional societies. In academic engineering, research and theory came to be emphasized and rewarded more than practical design experience. Modern physics used calculus, and in the 1890s some engineers tried to describe and solve engineering problems in the manner of physics problems. Their goal was to give engineering a more theoretical basis that would make design largely a matter of deduction from theory. Steinmetz shared the spirit of modern science in its search for general principles and exact methods. But he and other engineers in the electrical industry also recognized that the objects of engineering design had unique characteristics and that these also called for empirical understanding and guidance. Steinmetz and his colleagues in industry had to balance the academic ideal of open intellectual exchange with the proprietary need of industry to keep much of its knowledge secret. But Steinmetz was able to share his most important ideas, which were not proprietary, with the profession.32
Steinmetz’s success in developing standard formulas and methods of design ironically enabled General Electric engineers to do without him, and after 1900 he moved into the role of a consultant. At the start of the twentieth century, two new types of incandescent lighting, a metallic filament lamp invented in Germany and a mercury vapor lamp pioneered in New York City, began to compete with Edison light bulbs. In response, Steinmetz persuaded General Electric to establish a research laboratory in September 1900, where William David Coolidge (1873–1975) developed a method for making tungsten wire malleable enough to use in filaments. Tungsten is still used in light bulbs today. Irving Langmuir (1881–1957), a chemist who joined the General Electric Laboratory in 1909, extended the life of the tungsten filament bulb and for other work won the 1932 Nobel Prize in chemistry.
These researchers approached problems by seeking first to understand the basic physical and chemical facts and then by looking for ways to meet engineering needs. Their work exemplified the greater use of scientific knowledge to solve the more incremental problems that industry tended to have once its basic technology and business were established. The success of the General Electric Laboratory inspired the Westinghouse Company to establish a laboratory with chemists and physicists in 1916. General Motors incorporated Charles Kettering and his laboratory into its organization in the early 1920s, and the American Telephone and Telegraph Company created a new research institution, the Bell Telephone Laboratories, in 1925.33
The electrical discoveries of the early nineteenth century made it possible for Thomas Edison to create his network of light and power. But the science of his time did not encourage such innovation. By the 1870s, leading scientists and theoretically-minded engineers had concluded that the sub-division of electricity for light was impossible, and Edison would have never achieved his great innovation if he had been guided by such judgment. He was no tinkerer nor mere trial-and-error experimentalist; his novel conception of high resistance in the filament and low resistance in the dynamo proceeded from his radically new insight into the use of Ohm’s and Joule’s Laws. Edison achieved his breakthrough because he thought as an electrical engineer, not as an applied scientist.
After alternating current came into more general use, engineers with more formal academic training in mathematics and science then worked out a more theoretical grounding of the phenomena involved and made the new technology more efficient. Engineers such as Steinmetz recognized, however, that their work differed from science and that electrical engineering was not simply a matter of applying theory to practice.