TORQUE CONTROL SYSTEM FOR THYRISTOR MOTOR

PURPOSE:To transfer an operation mode continuously and smoothly without generating the dead time in torque polarity inversion by keeping DC currents at a fixed value on the transfer of the operation mode continuously changing DC voltage. CONSTITUTION:When an output from a speed regulator 8 is kept within a range of specified period width centering 0, the input/output characteristics of an absolute-value computing element 9a are determined so that an output from the computing element 9a is maintained at a fixed value. Accordingly, since DC currents Id are kept constant during a specified period including a zero point and DC voltage EdM rectilinearly alters during that time, the actual value of torque shifts approximately rectilinearly and the polarity of torque is changed over, thus generating no dead time DELTAt.