PRR MP54 - AC Cars For PRR Suburban Service

AC Cars For PRR Suburban Service

In late 1912, PRR engineers recommended large-scale electrification of PRR lines with alternating current (AC) at 11,000 volts and 25 cycles, starting with the suburban service along the Main Line between Philadelphia and Paoli. This project was authorized soon thereafter. In 1914 the PRR started adding AC electrical equipment to 93 MP54-type cars at the Altoona shops for use in this service. Each car received a pantograph, a transformer, a power truck, a motorman's cab and controls at each end, and MU circuits. These cars were then designated MP54E to distinguish them from non-electrified cars.

The Paoli line opened with electrical service in 1915 with great success, and other Philadelphia suburban lines were electrified in succeeding years. By 1933 the entire PRR line from Philadelphia to Penn Station had been provided with AC electrification and the lines from Philadelphia to Washington, D.C. and Harrisburg were subsequently electrified as well. MP54 cars then provided local service throughout this area. Large numbers of MP54 MU cars were obtained both by electrifying existing non-electrified MP54 cars and by purchasing and building entirely new cars. As improved electrical equipment was developed in later years, a numeral was added to signify the type of this equipment. Between 1926 and 1930 a further 144 cars were delivered from Altoona and Standard Steel in the class MP54E2. Between 1932 and 1937 a total of 41 "civil union" style married pairs were constructed by Altoona that consisted of an unpowered trailer class MP54T that that was towed by a motor car, class MP54E3, with 736 total horsepower compared with the normal 400. These special trailer motors could be identified by a small golden keystone above the number on the side of the car. They also had larger louvers on the side due to the greater demand for cooling air.

In time the need to change the car designations to distinguish between the non-electrified and electrified cars other than by adding an E became apparent, and it was decided to make the initial M be a "small" capital letter for the non-electrified cars. Small capital letters are awkward to use, so many books have used the LIRR scheme of omitting the initial M for the non-electrified cars (P54) while less commonly a lower-case m is used instead of the small capital (mP54).

In 1950, faced with the need for expensive new equipment for unprofitable suburban service, the PRR decided to extend the life of the MP54 cars instead of buying new equipment. The MP54s were rebuilt at the Wilmington electric shops with an initial batch of fifty 450-horsepower (340 kW) cars in the class MP54E5 and a follow-up batch of 49 508 hp cars in the class MP54E6 were rebuilt at the Altoona shops. (For unknown reasons, the designation MP54E4 was skipped.) In addition to the new, more powerful propulsion gear, other new equipment was installed including roller bearing equipped equalized trucks, new windows, and recessed transit-type lighting In 1951 there were a total of 481 AC MP54 cars of all types in service, consisting of 405 MP54, 42 MP54T, 10 MPB54B, 9 MPB54, 7 MB62, 4 MBM62, and 4 MBM62T cars.