It is interesting that in late 1892 the turbines were ordered four months before all the proposals were received for generators for local lighting and power. This was the era of the ‘Battle of the Currents’ with Edison as the leading proponent of direct current and with Westinghouse and others promoting alternating current. When the first execution by electricity took place in 1890 in New York State’s Auburn Prison, an ac electric chair was used. Dc proponents said the condemned murderer had been “Westinghoused.”i
Columbian Exposition 1893
The opportunity for a large scale demonstration of the alternating current system to dispel fears about the system’s high voltages and display its versatility came in the spring of 1892 when bids were taken to light the grounds of the Columbian Exposition to be held in Chicago in 1893. Westinghouse astounded everyone by bidding about one-third of the bid submitted by the recently formed General Electric Company. GE held the Edison incandescent lamp patents, a seeming crippling handicap.
Incandescent Lamp - Sawyer Mann Patent
However, Westinghouse owned the rights to an 1880 Sawyer-Man patent for a two-piece lamp, which had a glass globe and a cork-like ground glass stopper that didn’t infringe on the Edison patents.
Westinghouse Employees producing lamps for Columbian Exposition
In less than a year Westinghouse built a factory and produced a quarter million of these “stopper” lamps.
The Exhibition used more electricity than the whole City of Chicago.
4 of the 12 750Kw 2 ph Generators
The central-station plant that supplied the fair consisted of twelve two-phase generators rated 750 kW, 60 Hz, 2000 to 2300 volts, belt driven or direct driven by five reciprocating steam engines. The Westinghouse exhibit in Machinery Hall was the largest plant of the Tesla polyphase system operating at that time. In addition to the lighting plant, there was an exhibit of a complete polyphase system which showed power could be transmitted great distances, and then be utilized for various purposes.
500-hp 30-Hz 400-V 2-ph Generator
Taking power from the 60-Hz fair circuits was a 500-hp motor that drove a two-phase 500-hp, 30-Hz, 400-volt generator. This powered a 400 volt-to-10,000 volt step-up transformer, a short ‘transmission’ line, and a step-down transformer which ran induction motors, a synchronous motor
plus a rotary converter for changing alternating current to direct current.ii
The converter had a rotating armature with four slip rings for the two-phase ac and a commutator for the dc.iii
The Westinghouse polyphase exhibit was a big attraction when the Columbian Exhibition opened in the spring of 1893. Wooden models of the hydraulic turbines and governors under construction for Niagara Falls were also exhibited.iv
Columbian Exposition at Night
Representatives of the Cataract company had attended demonstrations of polyphase equipment at the Westinghouse factory and on May 6, 1893 adopted polyphase alternating current for both local use and transmission to Buffalo.v
Complications of the electrical design delayed awarding a contract for the generators. Transportation costs, import duties and patent questions removed the foreign manufacturers from competition.vi
The generator designs submitted in March 1893 by Westinghouse and General Electric did not fulfill the conditions imposed by the turbine designers for angular momentum and limited weight.
On August 10, 1893 new bids were requested based on a design by Professor Forbes of the Cataract company for a 20,000 volt two-phase generator with an external rotating field of the “umbrella” type whereas a rotating armature was standard practice.vii
The diagram shows the rotating field ring with the field poles and field windings. The armature winding was stationary. Westinghouse proposed two-phase; General Electric recommended three-phase.viii
Two-phase four-wire was selected because it was expected that much of the local load would be single-phase.ix
Next the frequency had to be selected. Hydraulic turbines had been ordered with a speed of 250 rpm. The frequencies possible at 250 rpm were: 16 2/3-Hz with 8 poles on the rotating field; 25-Hz with 12 poles; 33 1/3-Hz with 16 poles and 41 2/3- Hz with 20 poles. Low frequencies were preferred for large motors and rotary converters. Professor Forbes preferred 16 2/3- Hz for the commutating type ac motors then in use. Higher frequencies were more suitable for incandescent and arc lights. Tests had shown that at 25 Hz incandescent lamps did not show objectionable flickering. Westinghouse had adopted 60 Hz for lighting and 30 Hz for power and refused to guarantee efficiency at less than 30 Hz. General Electric recommended 41 2/3 Hz. Following a dinner meeting in October in New York City with Westinghouse representatives, President Adams of the Cataract Company asked Westinghouse’s chief electrical engineer if they could build and guarantee a 25-Hz generator.
Later in October revised proposals were received from Westinghouse and General Electric. Changes had to be made in the Forbes design. A 20,000-volt oil-cooled armature was not practical.x
On October 26 a contract was placed with Westinghouse for three 5000-hp, 25-Hz, 2200 volt, two-phase, four-wire generators.xi
This is a view of a generator armature at the Westinghouse factory. The armature conductors were insulated with mica, which was a fortunate choice because thermocouple tests in later years showed temperatures as high as 225C.
External Rotating Field Ring (poles (left arrow), coils (right arrow))
This shows a nickel steel field ring with two of the twelve poles and coils. Adams ‘Niagara Power’ book contains many pages detailing the design, manufacture, testing
and installation of these pioneering generators along with the auxiliary electrical apparatus including exciters, measuring instruments and switching devices. The testing of the first machine at the Westinghouse plant in Pittsburgh was probably the origin of the cardinal rule “Never place a short circuit on a piece of rotating machinery.” This was done during testing with great disturbance to the windings.
Cataract Construction Company - Board of Directors, Sept. 30, 1895
The first turbo-generator was successfully tested and operated in April 1895.xiii
The tall gentleman, No. 7, is John Jacob Astor and No. 8 is Edward Dean Adams, President. Schallenberger of Westinghouse designed a new type of switchboard indicating and integrating meters. On August 26, two-phase four-wire 2200 volts was first delivered commercially one-half mile to the Pittsburgh Reduction Company for reducing aluminum ore using the Hall process.xiv
This company became ALCOA, the Aluminum Company of America. The Carborundum Company, maker of silicon carbide abrasives, was another early customer.
The Forbes Subway, that served these early customers, was a concrete tunnel with cast iron racks on both walls for supporting the four copper conductor, rubber insulated, lead-covered cables in each circuit.xv
The use of low cost Niagara power enabled these companies, and other soon to follow metallurgical and chemical companies, to greatly reduce the cost of their products. Aluminum is a classic example.
In the mid 1800’s Napoleon III had a set of aluminum forks and spoons made for his most honored guests; less important guests used gold or silver tableware.xvi
In 1884 the cap for the Washington Monument was a 6¼-pound piece of aluminum, the largest made to that date in the United States. During 1905 and 1906 the Niagara, Lockport and Ontario Power Company used about 260 tons of aluminum overhead conductors to transmit Niagara power to Syracuse.xvii
By October 1896, when the third 5000-hp turbo-generator was placed in operation, the demand for electricity locally exceeded the capacity.xviii
Arrangements were made for additional capacity.xix
i. Adams, Niagara Power, 220. “dc distribution limits,” 76. Gardner Dales, “The Story of Nikola Tesla: The War of the Currents,” Tales from Gardner Dales (Western Division Historian, Niagara Mohawk Electric Company, n.d., photocopy), 17-22.
ii. “dc distribution limits,” 76. “Engineering the Electric Century: Polyphase ac systems come of age at the Columbian Exposition and Niagara Falls,” Electrical World, July 15, 1973: 30. Adams, Niagara Power, 2:193. Lewis B. Stillwell, “The Electric Transmission of Power from Niagara Falls,” Transactions of the American Institute of Electrical Engineers, 18, (1901): 457.
iii. George D. Shepardson, Electrical Catechism: An Introductory Treatise on Electricity and its Uses, 2d. ed., (New York, NY: McGraw-Hill Book Company, 1908), 387-390. “Polyphase ac systems,” 30.
iv. Adams, Niagara Power, 2:435.
v. Ibid., 74, 182, 194, 233.
vi. Ibid., 227.
vii. Ibid., 233, 419.
viii. Ibid., 235.
ix. Ibid., 236.
x. Ibid., 411-412.
xi. Ibid., 223-246.
xii. Ibid., 417.
xiii. Ibid., 39.
xiv. Ibid., 39.
xv. Ibid., 46.
xvi. World Book Encyclopedia, 1971 ed., s.v. “aluminum.”
xvii. Author’s calculation based on Ralph D. Mershon, “The Transmission Plant of the Niagara, Lockport and Ontario Power Company,” Transactions of the American Institute of Electrical Engineers, 26, Part II, (1907): 1277. Tower Department, Transmission Towers (Pittsburgh, PA: American Bridge Company, 1925), 171.
xviii. Adams, Niagara Power, 2:39.
xix. Ibid., 247.