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History of electric light

Chapter 38: THE SHUNT BOX SYSTEM FOR SERIES INCANDESCENT LAMPS
By Henry Schroeder
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Engineering & TechnologyHistory - Modern (1750+)

About This Book

A chronological, technical survey of electric lighting traces developments from early experiments with friction machines, Leyden jars and voltaic piles through advances in batteries, electromagnetic discoveries and the invention of the dynamo. It follows the parallel evolution of arc and incandescent illumination, outlining experimental filament and arc-control methods and the move to commercial installations and distribution schemes such as series, multiple and three‑wire systems. Later sections review later lamp technologies—Nernst, mercury‑vapor, gas‑filled and tungsten types—together with transformers, rectifiers, standardized voltages and sockets. The book is illustrated and includes a chronology, cost and usage statistics, and a selected bibliography.

THE SHUNT BOX SYSTEM FOR SERIES INCANDESCENT LAMPS

Shunt Box System, 1887.

Lamps were burned in series on a high voltage alternating current, and when a lamp burned out all the current then went through its “shunt box,” a reactance coil in multiple with each lamp.

Soon after the commercial development of the alternating current constant potential system, a scheme was developed to permit the use of lamps in series on such circuits without the necessity for short circuiting a lamp should it burn out. A reactance, called a “shunt box” and consisting of a coil of wire wound on an iron core, was connected across each lamp. The shunt box consumed but little current while the lamp was burning. Should one lamp go out, the entire current would flow through its shunt box and so maintain the current approximately constant. It had the difficulty, however, that if several lamps went out, the current would be materially increased tending to burn out the remaining lamps on the circuit. This system also disappeared from use with the development of the constant current transformer.