Steady-state behavior of carbon-pile regulators

ATTEMPTS TO MEASURE the steady-state characteristics of carbon-pile voltage regulators have been made repeatedly and have ended in failure because, upon increasing the voltage applied to the operating coil, a point is reached where the carbon-pile resistance no longer can be controlled by normal adjustments. It is not sufficient to attribute this result to lack of sensitivity in controlling the voltage. Instead the measurements reported upon here indicate that there exists an operating voltage above which the carbon-pile resistance jumps discontinuously to a high value.