| 摘要 |
PURPOSE:To eliminate a smoothing reactor of a speed control circuit by selecting the value of the switching frequency of a switching element to a value higher than the value of the frequency determined by the time constant of the armature circuit of a DC motor. CONSTITUTION:A controller 3 compares the counterelectromotive force of an armature 6 fed back through a voltage detector 7 with the voltage of a speed setter 2, thereby switching a switching element 4. In this case, when the inductance of the armature circuit 6 of a DC motor is represented by Lm(H), and the resistance is represented by Rm(ohm), the time constant taum of the armature circuit 6 is given by Lm/Rm. Then, the value of the switching frequency fs of the element 4 is selected to a value higher than the value of the frequency fm determined by the time constant taum of the armature circuit. In this manner, even if no smoothing reactor is provided in a load circuit, the current supplied to the armature 6 of the DC motor is not intermittently interrupted, but smoothed to the extent of causing no inconvenience. |
