Speed control of a D-C motor using a magnetic amplifier

Magnetic amplifiers are, similar to thyratrons, suitable for adjustable-voltage drives of d-c motors. While the operation with discontinuous armature current affects the motor characteristics undesirably, it offers in the lower power range an important economical advantage. After a discussion of the open-loop characteristics of the drive, the design of a medium-accuracy (5-per-cent) speed-control system for the fractional- and integer-horsepower range is explained where utmost simplicity and the use of inexpensive components are considered important design factors. Performance characteristics are given.