GB1322340A - Control systems - Google Patents

Abstract

1322340 Automatic speed control ASSOCIATED ELECTRICAL INDUSTRIES Ltd 25 Nov 1971 [11 Dec 1970] 58949/70 Heading G3R An A.C. error signal is used to trigger controlled rectifiers which supply unidirectional current to a motor, an output member of which determines by its position the value of a regulated parameter. In the circuit shown, an A.C. error 18 is added to a D.C. level set by a potential divider 31, Fig.1. If the error exceeds a threshold level, a unijunction field effect transistor 28 is turned on to supply pulses through inductors 30, 38, 39 to fire antiparallel thyristors 8, 9 or a triac in series with a D.C. motor (7), Fig.1 (not shown). The motor may control the brush position of a Schrage motor, an A.C. commutator motor or a continuous gearbox to regulate the speed of a ring spinning frame. The error signal is formed by a series of potentiometers, Fig.2, one of which, 15, is varied by the frame driving motor to indicate an actual speed value. The output from this potentiometer is an A.C. voltage which is opposed, i.e. in anti-phase, to outputs from potentiometers 14, 16, 17 which also contribute to the error signal 18. Potentiometers 14, 23, 26 are set manually, and potentiometers 16, 17, 27 are adjusted by cam followers in accordance with a program for controlling the frame through a complete cycle of operations.