The Mercury Arc Rectifier Applied to A-C. Railway Electrification

A new commutatorless motor with series characteristics has been developed and is briefly reviewed. The motor is particularly suitable for traction purposes and can be supplied from an overhead trolley at the usual a-c. electrification voltages and any commercial frequency. It is shown how it is possible, by the use of a grid-controlled rectifier, to eliminate not merely the commutator of the motor, but practically all of the expensive control, switching, and reversing equipment commonly used on a-c. and d-c. locomotives. Regenerative braking is also made inexpensive and practicable. The first part of the paper explains the general theory of the grid-controlled rectifier which is necessary for an understanding of the commutatorless motor. The data and layout of a 1,000-hp., 50-cycle, 15,000-volt, single-phase locomotive, now under construction, are given.