| 摘要 |
1353420 Automatic control of speed BORG - WARNER CORP 16 March 1972 [13 April 1971 22 June 1971] 12258/72 Heading G3R In a system in which at least two A. C. motors, e.g. driving separate but interrelated conveyers, are energized by respective inverters, the speed of one (the slave) is controlled with respect of the other (the master) by an arrangement in which the frequency of the slave inverter is adjusted by a voltage (on line 44) derived by combining (at 80) two ramp signals of opposite slope each produced (in digital-to-analogue converters 72, 85) by digital counters 67, 84 which count pulses produced by respective voltage controlled oscillators 26, 42 which also control the inverters, the counters and ramps being reset by respective signals from position detectors 47, 50 associated with each motor or its driven member. Thus, the members are driven in synchronism and the phase relationship between them is maintained at a fixed but adjustable value. Adjustment over a limited range is made by adding a voltage from a potentiometer 55 to the junction 80, but for adjustment over a wide range a pair of inversely connected potentiometers are used, one associated with slave detector 50 and the other with a second slave detector 250, spaced 180 degrees from the first. Change over from one to the other is effected by a switch, actuated by a cam on the potentiometer shaft, operating through logic circuits and transistor switches Fig. 6, (not shown). A further voltage is added or subtracted at the point 80 if the two drives are out of synchronism. This is detected in phase detector 60 by the occurrence of two consecutive master or slave pulses; a logic 1 is produced on line 111 and a 1 or 0 on line 112 according to whether the slave is over or under speed. These logic signals switch transistors connected to Zener controlled voltage sources in "out-of-sync" circuit 110, which is described Fig. 5, (not shown). Resister 99 provides a "setting up" adjustment to allow for the particular relationship of the frequency of position and inverter pulses. The detectors 47, 50, 250 may be magnetic or optical devices co-operating with appropriate spaced marks in respective conveyer belts. |
