| 摘要 |
PURPOSE:To prevent an armature voltage from becoming an overvoltage at field strengthening time by limiting a field current so that the counterelectromotive force of a DC motor does not exceed a rated voltage. CONSTITUTION:A field calculator 7 compares a speed feedback signal N with a speed reference signal N* to output a field control signal. A comparison discriminator 23 compares a speed reference signal before altering with a speed reference signal after altering, and switches a switch circuit 24 so as to become a speed reference difference to increase the field strengthening. Thus, a ramp signal for limiting the field current so that a counterelectromotive force from a field limit signal generator 25 does not exceed a rated voltage is output. Thus, it can prevent the counterelectromotive force from abnormally rising. |
