Several inventors had understood the principle of incandescent light. A filament of calibrated resistance is electrically heated to the surface temperature of the sun at which radiation is emitted at a wavelength corresponding to visible light. The challenges were developing a high-temperature material and creating a high vacuum, to prevent oxidation. After more than a thousand failures, Edison finally succeeded in 1879 by combining improved vacuum technology and a U-shaped baked carbon filament.

After more than a thousand failures, Thomas Edison created the electric lightbulb in 1879, combining improved vacuum technology and a baked carbon filament.

Edison was born in 1847 and lived until 1931. With his 1,093 patents he is recognized as history's most prolific inventor. He was self-promoting and fiercely competitive. He understood that inventions build upon the discoveries of others and that success requires a com-bination of experimentation, luck, hard work, and commercialization.

Edison had been home-schooled by his mother and was self-educated in science and technology. While working as a young journeyman telegraph operator, he had taught himself chemistry by repeating and modifying the experiments described by Michael Faraday.

His first inventions were techniques to transmit multiple signals on a telegraph wire. They were technologically brilliant, but commercial failures. He proclaimed that he would never give up, for he might have a streak of luck before he died. Edison next tried to extend the telegraph to a talking machine, but was beaten in 1876 by Alexander Graham Bell's invention of the telephone.

He immediately improved Bell's telephone. He next invented the phonograph by storing the mechanical vibration created by a voice on a wax cylinder. This sensational invention made Edison famous. He was invited to demonstrate the phonograph to Congress and to President Rutherford B. Hayes at the White House.

Edison was a quotable and inspiring public figure. While trying to invent the light bulb, he proclaimed that the first thousand tests had not failed, because he had learned a thousand things that would not work. Once successful, he noted that invention is 1 percent inspiration and 99 percent perspiration.

Edison's light needed an electric power supply. The Italian physicist Alessandro Volta first demonstrated a battery in 1800. By stacking alternative layers of dissimilar metals such as silver and zinc and an electrolyte, the energy from the chemical reaction is released in the form of electricity to an external circuit.

While representing the first steady source of electricity, a battery soon depletes and must be reprocessed or recharged. To be a practical replacement for candle, oil, and gaslight, Edison's light would need a more affordable, convenient, and sustainable electric supply.

Volta's battery had led to the 1820 discovery by Hans Oersted that electricity can produce magnetism. Ten years later, Faraday and Joseph Henry would show that, conversely, magnetism could produce electricity in a wire by either relative motion or by changing the strength of the magnet.

In 1837, a Vermont blacksmith named Thomas Davenport used the principle of electric-powered interacting magnets when he invented the first rotating electric machine, which is now called a brush and commutator direct current motor. It was later recognized that if this motor was driven in the direction of repelling magnetic forces, it would become a dc electric generator, or dynamo, converting mechanical to electric power.

Thus, a steady supply of electricity produced magnetically rather than chemically would be the key to the future. James Watt had spent 40 fruitful years developing steam engines to power factories and the industrial revolution. Use of steam engines for railroad locomotives followed. Edison's first utility would use steam engines to drive dynamos, producing electricity by magnetism.

He designed a system to serve 50 square blocks of lower Manhattan using coal-fueled boilers for the engines, which operated at 300 rpm. Six 500-kw electric generators would supply 33,000 lamps. He also predicted a potential for 750 industrial motors in the district. Thus, Edison's first utility would provide the dual functions of powering factories during the day and lights at night.

Despite major startup and operating problems, such as instability between parallel generators, Edison's 1881 central station for light and power became a public sensation and a prototype for other plants that would soon follow.

The Edison Machine Works, which would become the General Electric Co., was formed to manufacture generators and other electric apparatus. In 1886, Edison moved the factory from New York City to the small city of Schenectady, N.Y., in pursuit of lower labor costs.

Alternate Methods

A fundamental problem with Edison's direct current system was that there was no practical method to change the voltage. It generated, transmitted, and used the electricity at about 100 volts. Thus, a customer demand of 3,000 kw would draw 30,000 amps, which required large amounts of copper for conductors and also resulted in significant transmission losses. Edison's best solution to large losses and copper requirements was to build a generating station every few blocks.

George Westinghouse studied the Edison system and had a better idea. He had developed apparatus for gas pipelines that used the principle of high pressure for efficient transmission and then reduction to low pressure for safe use. A multiple voltage system would allow for generators to operate at medium voltage, transmission to be performed efficiently at high voltage, and end use to be at low voltage for safety.

George Westinghouse and Nikola Tesla combined their talents to harness the power of Niagara Falls for transmission to Buffalo, N.Y., 25 miles away, a feat many thought impossible.

A transformer could be used to increase the voltage at the generator for transmission and also to decrease the voltage for distribution and safe use. However, it requires alternating current. The principle is to convert input ac power to varying strength magnetism in the core that reproduces electric power by induction at the output. The voltage ratio is determined by the ratio of the output and input windings.

Westinghouse, who was born in 1846, was a mechanical engineer, inventor, and industrialist. Over his lifetime, he was awarded 360 patents and started 60 companies with a total of 50,000 employees. He would also serve as a president of ASME, in 1910.

He had grown up in Schenectady. With his four brothers, he had learned to design, manufacture, invent, and market at his father's Westinghouse Agricultural Works. It was 30 years later that Edison moved his factory to the same town.

Engineer, inventor, and industrialist were roles filled by George Westinghouse, ASME president in 1910.

After serving as a shipboard engineering officer during the Civil War, Westinghouse attended Union College. He started by inventing a device for returning derailed railroad cars to the tracks, followed by the air brake and automatic switching and signaling equipment and gas pipeline apparatus. Soon after Bell's invention of the telephone, Westinghouse invented an automatic switchboard.

He bought the patent rights to the Gaulard and Gibbs transformer that was not yet a practical device. It was inefficient and hard to manufacture. He reconfigured the core for lower losses and so that it could be more easily wound on a lathe. He first demonstrated a system using a transformer at Great Barrington, Mass., in 1886. A water-powered generator produced 500 volts, which was stepped up to 3,000 volts for one mile of transmission and then back to 100 volts for street lighting.

Besides flexibility in delivering voltage, another advantage of alternating current is that an ac generator is simpler than a dc generator. This is why an alternator is now used in automobiles despite a battery-based dc system. Spinning an electric magnet inside a fixed coil produces alternating current. Thus, electric power is produced in the stationary part or the stator. In a dc generator, the power is produced in the rotor and must be transferred to the external circuit by a continuous switching action via the brushes and commutator.

Steam turbines that operate best at high speed would later be developed as a more efficient, lower-maintenance, and compact alternative to steam engines. The simpler rotor of ac generators also would be more compatible with the high rotating speeds and centrifugal forces produced by a turbine drive.

A Motor for the System

There remained a major disadvantage to the ac system: There was no motor. Thus, the system could provide light, but could not provide mechanical power. A dc motor connected to an ac power supply would only overheat and burn out.

An engineering genius named Nikola Tesla had the answer. As a student, he had questioned his professor's teaching that an ac motor was impossible. He ultimately envisioned and built what is now called an ac induction motor. The electricity supplied to the stator sets up a rotating magnetic field that induces circulating current and thus magnetism in the rotor. No electric power is supplied by wire to the rotor. Thus, Tesla's ac motor would also be simpler to build and maintain, but much more challenging to analyze.

Tesla had worked for Edison, who refused to pay him as promised for some development work. Edison also ridiculed Tesla's ac motor and his proposal for a multiple-phase ac power system.

Nikola Tesla's ac induction motors were a key to the success of Westinghouse's ac system and proved simpler to build than dc motors.

Westinghouse recognized that Tesla's motor could provide the ac system with an absolute advantage over Edison's dc system. In 1888, he traveled to New York to meet Tesla. He bought the patent rights and retained Tesla as a consultant.

The motor was further developed for higher capacity and efficiency, but a frequency standard for an ac system had not been established. Lights would flicker at low frequency. Undesirable lag of current relative to voltage occurred at high frequency. Our present-day standard of 60 cps was established as the best compromise. The generation and transmission on three wires, or phases, separated by 120 degrees was defined as the best use of transmission lines and the preferred power supply to induction motors.

Ultimately, Tesla's ac motor became highly preferable to a dc motor. Every factory machine could have its own motor. It has been noted that in a modern home, the number of induction motors that quietly and reliably power our conveniences and comforts is comparable to the number of light bulbs.

In addition to being an electrical genius, Nikola Tesla had a taste for publicity, as shown in this staged photo of high current travel from a coil to a transmitter.

Many cities and villages were planning for electrification. The Westinghouse ac system began to get most of the orders rather than Edison's more expensive, higher-maintenance, and less efficient dc system. Edison's best remaining argument was that the high voltages that made the ac systems more efficient also made them too dangerous.

The New York State Legislature inadvertently gave Edison one last opportunity for negative advertising by seeking a more humane method to execute criminals than by hanging. Death by electricity was suggested. Edison had previously expressed his disapproval of capital punishment, but he was now desperate to discredit the competition. Thus, he was receptive when an engineer named Harold Brown offered his services to demonstrate the dangers of ac by using it for execution.

Edison made his lab available. Brown, after electrocuting a variety of animals, pronounced ac electricity a perfect medium for execution. Brown acquired three Westinghouse generators and designed the first electric chair, which he sold to the state for $8,000.

In August 1890, after two failed attempts, a convicted murderer named William Kemmler became the first person to be executed by electricity. When a name was sought for the new execution technology, Edison suggested "Westinghoused."

George Westinghouse responded by eloquently defending the safety of high voltage, with the proper safeguards, and commending its ultimate benefits to society.

Electrocution failed to help Edison and his dc system. He sold his interests to the newly formed General Electric Co., which would produce ac equipment under cross licensing with the Westinghouse Electric Co.

About 300 miles from Westinghouse's hometown of Schenectady was the largest single potential source of hydropower in the United States, Niagara Falls.

It sat not far from Buffalo, N.Y., which had grown into a major city as the western terminal of the Erie Canal, which was completed in 1825.

Niagara Falls, with its 180-foot drop and flow rate of 12 million cubic feet per minute, had a potential of 4 million hp or 3 million kW, but it was 25 miles from Buffalo. For more than a half-century, methods such as a system of belts, driveshafts, and compressed air had been considered but found to be impractical to transfer power over this distance.

Westinghouse's new electric system was regulated by control panels such as this one.

High-voltage electric power transmission offered a new possibility for harnessing large amounts of power at one location for use at another. Despite much skepticism about the feasibility, Westinghouse won the contract to install the large-scale system that he and Tesla had envisioned. In 1896, the first 15,000 hp was delivered from Niagara Falls to Buffalo.

As the system expanded, Buffalo became known as the City of Light. In 1901, it hosted the Pan-American Exposition, which highlighted the marvels of electricity. The tragedy that would occur was not from high voltage, however. President William McKinley, a personal friend of George Westinghouse and a fellow Civil War veteran, visited the Exposition. The President was assassinated by an anarchist while shaking hands in a receiving line.

The Wizard of Schenectady

Like steam engines, electricity was both mysterious and marvelous. A century earlier, steam engines were built and operated before concepts of heat and temperature were defined. Thermodynamics as a discipline was largely developed to help describe and ultimately to improve the operation of engines and related energy conversion processes. Similarly, engineers such as Westinghouse and Tesla designed the first transformers and motors without the benefit of mathematical methods.

Charles Proteus Steinmetz responded to the need for analytical tools. He was physically deformed, a hunchback who had studied math, science, and engineering before fleeing Germany to escape political prosecution for his socialist political views and activism. He joined the newly formed General Electric Co. in 1892.

Charles Steinmetz, who became the Electrical Wizard at GE after coming to the United States from Germany, was honored by a 1983 postage stamp.

Over the next 30 years, Steinmetz would become world-famous as the Electrical Wizard of Schenectady while also teaching at Union College. He developed the rotating phaser method for representing ac systems. He wrote textbooks and articles. His 195 patents secured a place for him in the Inventor's Hall of Fame. He also maintained his political views by serving on the city council under a socialist mayor and as the school board president with the goal of a lunch and a desk for every child.

By the 1930s, electricity, which was originally considered a luxury, was being argued to be a basic human right and vital to the strength of the nation. When Edison died in 1931, someone suggested that electricity be turned off for a few minutes as an act of recognition, but it was deemed too vital to the country for even a short interruption. Meanwhile, electricity was still a distant dream in most rural areas and on farms. The electric utilities were private industries. The cost of transmission and distribution to the low-population-density countryside was not justified.

Federal Projects

Accordingly, Congress created federally funded projects, such as the Tennessee Valley Authority in 1933 to harness rural rivers for electric power while providing navigation and flood control. This was followed by the Rural Electrification Act of 1936 to provide low-interest loans for transmission and distribution in rural areas.

Electric power to the countryside ultimately resulted in connecting the previously isolated systems in cities, towns, and villages. By 1950, virtually all of the United States was interconnected and operating at 60 cps.

The resulting system can be described metaphorically as a pool in Kansas to which all generators are pumps that are supplying water and all users are drawing water. Supply must equal demand. An increase in demand will temporarily lower the level, which results in a command for the most cost-effective pump to supply more. A decrease in demand temporarily raises the level or increases the system frequency and thus calls for the highest incremental cost generator to produce less.

Changing Demographics

Edison's utility effectively turned night into day and also powered factories. Subsequently, electricity has revolutionized life by supporting refrigeration and air conditioning, radio and television, and the new information age, while changing the demographics of the country and the world.

A farmer previously labored hard to milk six cows by hand. With an electric-powered milking machine, he could increase productivity to 60 cows. Surplus labor left the farms. With the advent of electric air conditioning over the last 50 years, all parts of the country can be comfortable year-round, allowing large migrations of people from the North to the South.

Our remarkable modern electric power system still has room for improvement. The transistor was invented in 1947 and led to the microchip, which would become the building block of computers. The same technology also led to solid state power switching devices in the form of rectifiers, inverters, frequency converters, and the ability to step up and step down dc voltage similar to a transformer on an ac system.

These devices have been used primarily to correct some of the disadvantages of ac systems, such as variable speed control for motors and improving the typically lagging phase angle between current and voltage.

The best power system for the future could better use solid state power electronics. Generators would remain ac, but with more efficient continually variable speed capability, rather than the fixed 60 cps synchronous speed. Transformers would step up the ac power voltage, which would then be rectified to high-voltage dc for higher-transmission capability and lower losses. At the distribution level, solid state devices would reduce the dc power to low-voltage dc for safe use and better interface compatibility with various distributed generation devices, such as photovoltaics, wind turbines, and fuel cells.

Thus, the power system of the future could combine the best features of the original Edison and Westinghouse systems.

Franks Wicks, a frequent contributor to Mechanical Engineering, is a power engineer and a professor of mechanical engineering at Union College in Schenectady, N.Y.

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