The electric streetcar is often called a "trolley" because of the design of its power-delivery system. Electrical current is sent to the streetcar's motor by way of a pole atop the streetcar. At the end of this pole is an electrical contacting device called a "troller" (hence, the name "trolley") that rolls along a suspended wire above the street. Contact is maintained along the wire above a dual track laden route on which the streetcar moves. Transferred along the copper wire is direct current (DC) that usually originates from a steam or a hydroelectric power house.
The city of Mechanicville, located on the Hudson River north of Albany, New York, had one such hydroelectric power house that delivered power for more than just electric light in the early 1900s. The Mechanicville Hydroelectric Station also supplied power to the Union Traction Company of Albany, as well as to the Schenectady Railway Company. What came from that powerhouse were 12,000 volts (V) of alternating current (AC) that was transferred along high-tension lines into any of the surrounding cities. There, substations would step-down the current from 12,000 VAC to 600 VDC. This latter measurment was the standard delivery for most trolley systems throughout the U.S. at the time.
Direct current was the preferred current for trolley cars because DC had better torque and was better for controlling streetcar speed. The 600 VDC had only a short distance to travel from substation to inner-city trolley car, but it was a different story for trolley cars that spanned the distance between two cities. (These trolley cars were known as "interurbans".) The problem with DC running along copper wire is that direct current can only go a short distance. But any interurban trolley car traveling out of the city center and along lines into the country required a current that could travel through copper wires for much longer distances.
Alternating current had the capacity to do so. Thomas Edison's new business, the General Electric Company based in Schenectady, New York, saw the benefits in owning a streetcar company and experimented with streetcars that used AC. In 1904, an exhibition run of an alternating current trolley made its successful debut.
Editor's Note: Part 6 of this multi-part series will run in two weeks.
Previous Blog Entries in This Series
The American Streetcar (Part 1)
From Stagecoach to Streetcar (Part 2)
From Horse-Drawn Streetcars to Cable Cars (Part 3)
The Birth of the Electric Streetcar (Part 4)
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