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Chapter 13
Switchmode Systems
Early DC generators employed an excitation system that was con-
trolled by a “tick-tock” regulator. If the generator voltage fell below
the regulated value, the excitation was switched on until it was back to
normal. Then, the excitation was switched off again, and the field cur-
rent free-wheeled through a shorting contact. The field time constant
was long enough that this simple regulator was entirely satisfactory to
maintain generator voltage within a narrow band. Until transistors
came along, such a simple system regulated the voltage for the instru-
ment cluster in an automobile, and one could occasionally see a ...