| 摘要 |
PURPOSE:To lighten the burden of reactive currents by detecting reactive power and excitation frequency and opening and closing a capacitor for correction by using a switching circuit. CONSTITUTION:In a driving circuit for an ultrasonic motor, capacitors C1, C2 for correction are connected in parallel with electrostatic capacity by switching transistors(Trs) 3, 4 by employing a comparator 12, thus reducing reactive currents. A reactive current section and DC voltage corresponding to excitation frequency are applied to the input-section non-inverting side of the comparator 12, and a reactive current section opening and closing the capacitors C1, C2 for correction and DC voltage corresponding to the point of excitation frequency are set to all inverting side input. The comparator 12 conducts the Trs 3, 4, and the capacitors C1, C2 for correction are connected in parallel with stator equivalent circuits 9, 10. Accordingly, the variable speed range of the motor is spread, thus driving the motor by sufficient current capacity. |
