Abstract
The interruption of d-c coil circuits can cause voltage surges destructive to rectifiers. The origin of these surges is discussed, and the use of shunt-connected devices for surge control is described. Calculation methods are given for determining the necessary component values for any required degree of surge reduction, and the time to reach drop-out current with those components. Calculated results obtained by these methods are compared with those shown in the oscillograms.

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