| 摘要 |
PURPOSE:To enable to detect overload highly sensitively in response to the state of driven systems by judging the occurrence of overload when the conduction angle of a silicon-controlled rectifying element exceeds a specified value based on the interrelationship between the number of revolution of a motor and the conduction angle. CONSTITUTION:The revolution speed of a motor 2 of an electronic sewing machine and the like is sensed by providing, for example, a light-emitting diode 11 and a photodiode 12 on both sides of a slit disk 13 attached to a rotating shaft 3, and the resultant pulse signal P1 is input to a microprocessor (MP)4. The conduction angle of a bidirectional SCR 10 is controlled by the phase-control data PCD from the MP 4, thereby the revolution speed of the motor 2 operated by a commercial power supply 6 is controlled. During the period the MP 4 is executing other subroutine, the overload sensing is performed with appropriate timing. When the conduction angle of the SCR 10 exceeds the upper limit based on the interrelationship between the revolution speed of the motor 2 and the conduction angel, the overload is recognized in accordance with a predetermined program, and a routine such as emergency stop is executed. |
