Electrification in the 1890's replaced mules and steam locomotives with clean quiet DC power and electric motors built in to the cars. Much of the power for the streetcars came from NOPSI's then new Market Street power plant. (1901). The streetcar system continues to draw its power from the city's commercial power suppliers (now Entergy).
Special RTA substations transform the power from 60 hz alternating current at distribution voltages (typically 13,800 volts) to the 600 volt DC used by the electric motors in the cars. Overhead power lines, called catenaries deliver the power to the cars through a trolley pole connection.
Each car uses two 65 horsepower GE or Westinghouse traction engines to provide locomotion. 65 HP is equal to 48 KW assuming 100% efficiency. Each motor can consume 48,000 watts / 600 volts or 80 amps at full power. Two motors could consume 160 amps. If the transformer is capable of producing 1200 amps it would be able to power 7 cars at full acceleration simultaneously. This is enough to power 21 cars in average operation.
Substations are required around the city to keep the current on the wires down to reasonable levels so they don't melt from resistance (I2R) losses. The more current that flows the hotter the wires get. The conductor wire used in the catenaries is (what? aluminum or copper, how many circular mills (AWG)).
Cars also consume power to compress the air used by their pneumatic braking system and in the later model the pneumatic operated doors and to power headlights and internal lighting. How much of this parasitic load is there?
A typical substation like the one at Valence and Loyola pictured in the satellite view (click the Satellite button) contains the 850 KVA transformer-rectifiers. The source below says each transformer rectifier can produce up to 60 amps (why is this so low? at 850 KVA and 600 volts dc more amps ought to be available ---- 850,000 /600 volts is 1400 amps.)
In 1909 a new electrical
substation was constructed on the corner of Valence and Loyola Streets.
The Valence Substation, located approximately midway along the route of
the St. Charles line, provided the 600volts DC electricity for the
streetcars. There were three transformer-rectifiers each rated at 850
KVA at 13.8 Kilovolts, 60 Hertz, input, and about 60 amps, direct
current output. Two of the transformer-rectifiers were used, with the
third unit kept as a spare.
...Lynn
NOTE: (From "The St. Charles Street Car or the New Orleans & Carrollton RailRoad", written and
Published by James L. Guilbeau in 1975, revised and reprinted in 1977), and 3rd Edition, "
The Saint Charles Streetcar or the history of The New Orleans and Carrollton Railroad" published by the Louisiana Landmarks Society, Pitot House, 1440 Moss Street, New Orleans, La. 70119)