| 摘要 |
PURPOSE:To constitute a close loop and to hold an exciting current in a constant state, by a method wherein the energization to the exciting coil is controlled to turn ON and OFF it by means of a duty cycle into which a deviation between a value of a current flowing to the exciting coil and a reference value is converted. CONSTITUTION:An output of an AC power source is rectified by a rectifying circuit 21 to input it to an exciting coil 18 through a switch 19. A current flowing to the exciting coil 18 is detected by a current detecting resistor 23, a deviation between the detecting value and a reference value 28 is found by a deviation amplifier 35 to input the result to a switch driving circuit 26. A deviation value is converted into a duty cycle by the switch driving circuit 26, and the switch 19 is controlled to turn ON and OFF it according to the duty cycle. |
