| 摘要 |
PURPOSE:To remarkably reduce a smoothing capacitor when a 3-phase AC power source is employed by holding an armature current at a set value by a chopper circuit. CONSTITUTION:Since a voltage drop of a resistor 13a is proportional to the armature current of an armature coil 4a, it becomes armature current detecting means. If the voltage drop of the resistor 13a exceeds the voltage of a reference voltage terminal 15, a transistor 10a is interrupted, magnetic energy stored in an armature coil 4a is discharged through a transistor 10b, the resistor 13a and a diode 12d, and the armature current is reduced. If an input of one terminal is dropped to a predetermined value by the hysteresis characteristic of an operational amplifier 14a, it is again returned to a high level, and the transistor 10a is conducted. Accordingly, when the armature current of the coil 4a is increased and increased to a set value, the transistor 10a is again interrupted, and the armature current is gradually reduced, and held at a restricted value. |
