GB967558A - Means for regulating the speed of a driven shaft - Google Patents

Abstract

967,558. Automatic speed control. NECCHI S. p. A. Dec. 5, 1961 [Jan. 13, 1961], No. 43447/61. Heading G3R. [Also in Division F2] In a control system for regulating the speed of a shaft driven through an electromagnetic clutch, the output voltage of a tacho-generator associated with the shaft is applied to the magnetising winding of an electromagnetic brake acting on the shaft whereby the braking effect is varied as the speed varies so that the shaft speed is maintained constant. As shown, an A.C. motor 1 drives a shaft 3 through an electromagnetic clutch 4 the magnetising winding of which is connected, over a contact d of switch 14, to a voltage derived from a rectifier 9 fed from the motor supply circuit. The shaft 3 drives a load 5 and a tacho-generator 19 the output voltage of which is applied, over contacts d<SP>1</SP> and d<SP>11</SP> of switches 17 and 18, to the magnetising winding of a brake 16 acting on the shaft 3. In operation, the shaft 3 is driven so that there is some slip in the clutch 4; if the load 5 then increases, the speed of shaft 3 tends to decrease so that the output voltage of generator 19 and excitation of brake 16 also decrease whereby the shaft speed tends to remain constant. Conversely, the braking effect increases with decrease in load. An amplifier, e.g. a transistor amplifier, may be included in the electrical connection between the generator 19 and the brake 16 (Figs. 2 and 3, not shown). The switches 14, 17 and 18 are provided with other contacts a, a<SP>1</SP>, a<SP>11</SP>, b, b<SP>1</SP>, b<SP>11</SP>, and c, c<SP>1</SP>, c<SP>11</SP>, so that the shaft can be driven with no slip in the clutch and with the brake de-energized, can be stopped by the brake with the clutch de-energized, or can be free with both clutch and brake de-energized. Specification 927,630 is referred to.