CURRENT LIMITING CONTROL METHOD FOR SPEED CONTROL DEVICE USED IN DC MOTOR AND SPEED CONTROL DEVICE FOR DC MOTOR FITTED WITH CURRENT LIMITING CIRCUIT

摘要

PURPOSE:To prevent the flow of an excessively large current in the DC motor, by detecting the rise of the power supply voltage by utilizing the existence of phase difference between interline voltage and phase voltage and controlling so as to limit in advance the conduction angle of the phase control circuit. CONSTITUTION:When the power supply voltage rises sharply, interline voltages e1, e3, e5 having 30 deg. phase lead rise, and e5 becomes higher than output e7 of peak maintaining circuit 11, which maintains peak value e7 of e6, which is the resultant of the attenuation and rectification of phase voltage e2 before the voltage rise. By this, the difference e5-e7 is outputted from voltage comparator 15. As a result, phase angle clamping circuit 16 operates, and thereby the conduction angle of the switching element of power converter 5 is checked in advance.