The Collection of Current From Overhead Contact Wires

Up to a few years ago, the generally accepted limitations for the amount of current which could be collected from an overhead distribution system were from 300 to 800 amperes in heavy interurban service and between 800 and 1000 amperes, with a maximum of 1500 in the case of the Chicago, Milwaukee, & St. Paul. It is not possible to determine the limits of current collection by theoretical calculations nor by the experience on any particular installation. The tests described and analyzed in this paper were demonstrated on a four-mile track using special overhead construction of the twin trolley type with observation towers at several points to enable observers to carefully inspect commutation between the collector and the trolley wire. Tests were also made to determine the temperature rise which would be obtained as a result of delivering, for a period of five minutes, a current of 5200 amperes to a standing locomotive. Further tests were made to determine what damage would result, if any, should a pantograph leave the wire while delivering currents as high as 4000 or 5000 amperes. Test data are included and description of the several types of overhead construction used.