GB981754A - Improvements in or relating to devices for synchronising a rotating system - Google Patents

Abstract

981, 754. Automatic speed control. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. March 22,1961 [March 25, 1960], No. 10444/61. Heading G3R. For phase control, positive control pulses from a rotating member and negative reference pulses are separately applied to terminals 1, 2, associated with the input of a multivibrator 5 having its square wave output voltage applied to the grid of triode 14. A square wave voltage having the same polarity as the input pulse is developed at the cathode of the triode 14. When a positive pulse appears, capacitor 22 is charged through rectifier 21, a negative pulse causing the capacitor to discharge through resistor 23. In this manner, a sawtooth voltage is developed across capacitor 22 which is connected to capacitor 25 through rectifier 24, the capacitor 25 being connected to a positive supply terminal through resistor 19. The average voltage across the capacitor 25 is a measure of the phase difference between the two pulse series and forms a control voltage for maintaining synchronizm. If the positive pulses tend to lag the negative pulses, the voltage across capacitor 25 decreases so that more current is passed through coil 32 which is in circuit with double triode 26. The rotating member is driven by a motor through a magnetic coupling whose energizing coil 32 increases the speed of the member when the excitation of the coil is increased. When the control pulses lead in phase, the reverse effect occurs. Upon starting the rotating member, a capacitor 11 in circuit with the multivibrator 5 is charged to such a voltage that the positive pulses applied to terminal 1 do not become effective, and the output of the multivibrator is such that the member is driven with maximum torque and its speed rapidly approaches the desired value. The control voltage across the capacitor 25 becomes operative only when synchronizm is reached and the phase control becomes effective. During starting, the voltage across the capacitor 25 is always so low that the current through the coupling coil 32 is at a maximum.