| 摘要 |
PURPOSE:To prevent an excess over the dynamic range of a D/A conversion circuit and the impossibility of control by generating applied voltage and reducing an analog signal only by the section of applied voltage when the analog signal exceeds the set voltage or more of a load current detector when load as disturbance is applied to a motor. CONSTITUTION:When load as disturbance is applied to a motor 25, the number of revolution corresponding to the frequency of a reference speed signal 1 intends to be kept. The value of an analog signal 4 rises and intends to exceed the dynamic range of a D/A conversion circuit 22, but applied voltage 5 is generated before the value of the analog signal 4 exceeds the dynamic range of the D/A conversion circuit 22 by previously bringing the set voltage 8 of a load current detector 27 to a value slightly smaller than the value of a current conversion voltage 7 at a time when the value of the analog signal 4 exceeds the dynamic range of the D/A conversion circuit 22, and applied voltage 5 is applied to the analog signal 4 in a summing amplifier 23. The analog signal 4 is reduced only by the application of applied voltage 5. Excess over of the dynamic range of the D/A conversion circuit 22 of the analog signal 4 and the impossibility of control can be prevented. |
