摘要 |
PURPOSE:To eliminate the need for a special oscillator for modulating a braking signal, and to change a braking force smoothly by changing over the reference voltage of a differential amplifier from a speed command to a braking command when receiving the braking signal. CONSTITUTION:When a braking signal is input, a changeover circuit 70 outputs a braking command output from a braking force setter 63 to a differential amplifying circuit 72. The rotational speed of a rotor is detected successively by a speed detector, and output as a speed signal to the differential amplifying circuit 72. The differential amplifying circuit 72 takes the difference between the braking command and a speed signal, and a signal of pulse width corresponding to the difference is output from a pulse width modulation circuit 81. Accordingly, the difference of the braking command and the speed signal is increased with the decrease of the rotational speed of the rotor by braking, and the braking force is augmented regulated by the braking command. |