| 摘要 |
PURPOSE:To accurately stop a load to predetermined stopping position without necessity of a mechanical stopping mechanism by conducting a thyristor connected to one coil of an AC motor to flow pulsating current through the coil to brake the motor. CONSTITUTION:When a signal ''1'' is supplied from a pulse generator circuit 53 to a rotation indicator 10 in the shown state, the outputs of gate circuits 26, 27 are together inverted to 0 to allow transistors 32, 33 to be conducted so as to conduct photocells 46, 47. Thus, thyristors 49, 50 are conducted responsive to the polarity of an AC power supply 52 to rotate a rotor 9c. When a rotor 10 driven by a motor 9 rotates at 180 deg., reed switches 20, 21 are inverted to allow oneshot pulse generator 29 to produce a pulse to cut off the transistor 32 and to conduct the transistors 31, 33, conduct thyristors 49, 51 so as to flow half-wave rectified current through the coils 9a, 9b to permit the rotor 9c to be braked and stopped. |
