Patent GB-601143-A (GB)
Title: Improvements in electrical governors
IPC: H02P29/00
Filed: 1945-12-22
Abstract: 601,143. Automatic control systems for clutches. WINTHER, M. P. Dec. 22, 1945, No. 34863. Convention date, May 16, 1942. [Class 38 (iv)] In eddy current clutch control apparatus, the clutch D.C. field is energized from an A.C. source by at least one power rectifier valve which is grid-controlled by an amplifier, grid controlled from a second rectifier valve operating in conjunction with a generator associated with the driven member. In the embodiment shown, the single-phase transformer AT supplies the half-wave, gas-filled, grid-controlled rectifiers RT-1, RT-2 which energize the winding CL of the clutch. Firing of rectifiers RT-1, RT-2 is controlled by the gridcathode potential comprising an A.C. component produced by transformer KT-1, the primary of which is supplied from heater transformer KT " Scott-tee " connected across lines L-1, L-2, L-3 and a D.C. component from lines 51, 52. The grid voltage A.C. components lag 90 degrees relative to the respective anode voltage of valves RT-1, RT-2, and the resistors BR limit the grid current. The permanent-magnet A.C. generator AL operated by the clutch-driven member produces a D.C. voltage proportional to its speed between points BG, ED through transformer PL-2 and full-wave rectifier RE-2. A second fullwave rectifier RE1 in conjunction with beam power tube 6 produces the reference D.C. voltage, a proportion of which is tapped off, by potentiometer P-10 and applied, with the opposed voltage across BG-ED to the grids GL, GR of the amplifier valve 3 over the lines 54, 58. The anodes of valve 3 are connected by resistors 25, 26 and joined to the grids G and cathodes K, respectively of valves RT-1, RT-2 by leads 51, 52. Power to valve 3 is provided by full-wave rectifier 30 and transformer T-R at the cathode and the common point of resistors 25, 26. In operation a positive potential is maintained on grid GR of valve 3 by adjustment of potentiometer P-10 which selects a reference voltage and determines the datum speed of the clutch-driven shaft. Anode R conducts, and thereby renders the lines 51, 52 positive and negative respectively and positively biasses valves RT-1, RT-2 which conduct, energize coil CL and tighten the clutch coupling. A rise in the speed of the driven shaft causes an increase in the negative voltage opposing that developed across potentiometer P-10 and the grid GR becomes negative and grid GL positive. Anode R ceases to conduct and anode L becomes conducting, thus wires 51, 52 become negative and positive respectively, the valves RT-1, RT-2 are negatively biassed, cease to conduct and lower the excitation of coil CL which affects a reduction in the speed of the driven member. The sequence is reversed upon a fall of shaft speed. To reduce the effect of changes in the supply voltage upon the system through the medium of the reference voltage, a thermionic stabilizing circuit is employed between the rectifier RE-1 and the potentiometer P-10 as described in Specification 601,144. Similarly, the H.T. supply to the amplifier circuit is stabilized by means of a cold-cathode discharge tube. Specification 576,620 also is referred to.