Low-frequency Phase-shifting Device Using D.C. Motor and Its Characteristics
Kokichi NITTA, Hiroshi OKITSU, Yasuo Kondo · Transactions of the Society of Instrument and Control Engineers · 1965
In many control systems, there are often used low-frequency phase-shifting devices such as phase lead devices to get quick response or phase lag devices to prevent steady state error between input and output signals. Especially, in d.c. control systems, frequencies of input signal are usually in the range of 0.001∼a few cycles per second, so satisfactory result can not be obtained if using conventional CR phase-shifting device. In this connection, separately-excited d.c. motors with comparatively large time constant may be used instead of static condensers. Characteristics of d.c. motoers, however, is not exactly equal to that of static condensers, but is expressed as the combination of a static condenser and resistors. In this paper, equivalent circuit and dynamic characteristics of this device are discussed in detail.