GB1290515A - - Google Patents

Abstract

1290515 Automatic tension control MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 17 Nov 1969 [20 Nov 1968(2)] 56244/69 Heading G3R Variations in tension of yarn being wound on a spool driven by a three-phase induction motor are detected by vertical movements of a roller operating a differential transformer the rectified output of which is compared with the output of a tachometer generator associated with the motor so that any difference is effective to vary one phase of the supply to the motor to correct the tension. As described, the tension of yarn being wound on a spool driven by a three-phase motor 15, Fig. 2 determines the vertical position of a roller (not shown) which adjusts the position of the core 42 of a differential transformer 12 supplied by a transistor oscillator-amplifier 24, 34. Variations in tension from a desired value produce an output from transformer 12 which is rectified at 13 and added algebraically to the rectified output of a tachometer alternator 18 driven by motor 15. The resultant voltage adjusts, through a transistor 56, the phase of pulses produced by a uni-junction oscillator 55 and applied through a transformer 59 to a bi-directional thyristor 51 or a pair of unidirectional thyristors in series with one phase of the supply to motor 15 so that motor speed is varied and tension restored to the desired value. The supply to transistors 55, 56 is obtained from the three-phase source through a rectifier 52 and a supply from the same source may replace battery 20. In an alternative arrangement, the A. C. terminals of a bridge rectifier are connected in series with one phase of the supply to the motor and a controlled unidirectional thyristor connected across the D.C. terminals of the rectifier.