Abstract

In commercial d.c. arc power supplies using a motor-driven variable reactor; it is not possible to predict accurately the excitation current before the arc is started. To permit pre-arc setting of the current, a circuit (Figure 1) is in use which temporarily shorts the d.c. so that its level can be adjusted. The circuit requires two relays which are energized by a single switch. One relay pulls in fast and drops out slowly; the other pulls in slowly and drops out fast. The fast-in, slow-out relay R₁ is used to disconnect the normal output and timing circuits and to short the d.c. output internally. The slow-in, fast-out relay R₂ connects the primary input power to the rectifier circuit. The relays can be time-delay types using hydraulic or pneumatic principles for delay, or they can be fed through RC networks as shown in Figure 1.

A Combination Arc-Spark Source for Magnesium Analysis*

V. J. Caldecourt and J. L. Saunderson
J. Opt. Soc. Am. 36(2) 99-102 (1946)

A Condensed Arc Source Unit for Spectrochemical Analysis

D. A. Sinclair
J. Opt. Soc. Am. 38(6) 547-553 (1948)

A D.C. Arc Source and Automatic Controller*

G. H. Fetterley and W. M. Hazel
J. Opt. Soc. Am. 40(2) 76-79 (1950)

The Arc and Spark Spectra of Gadolinium

Henry Norris Russell
J. Opt. Soc. Am. 40(9) 550-575 (1950)

Zeeman Effects in the Arc, First Spark, and Second Spark Spectra of Yttrium

J. Rand McNally and George R. Harrison
J. Opt. Soc. Am. 35(9) 584-596 (1945)