| 摘要 |
An electric device for the control of yarn feeding devices for weaving machines, of the type providing for the presence of a yarn supply wound onto a drum and comprising an electric three-phase driving motor, wherein, in order to change the speed of the motor, this latter is supplied with AC voltage, phase controlled by triacs. For this purpose, three signals are used representing a selected speed for the motor, the true speed of the motor itself and, respectively, the presence of the yarn supply on the drum, these signals being compared and processed into an electronic circuit, in order to produce signals forthe control of the triacs. The three signals are compared in a circuit generating a signal which must in turn be compared with three periodic ramp signals having the same phase and a period half those of the three supply voltages of the motor, in order to generate square wave signals for energizing the corresponding triacs. |
