| 摘要 |
PURPOSE:To suppress a rush current in case of starting by providing PWM control means in a PAM control type inverter, and PWM-controlling a main switching element of an inverter only at starting time. CONSTITUTION:When a frequency setter 5 generates a speed signal (a), a compa rator 9 raises an operation stop signal (e), a lamp circuit in a controller 10 generates a lamp signal (f) in response to the signal (e), and a frequency station ary signal (g) is input to the setter 5 to stop the voltage rise of the signal (a). The pulse signal (b) of a voltage/frequency converter 6 of the period for PWM- control in this rise stopping period is input to an integrator 12, which outputs a triangular signal (i), which is input to a comparator 13 to be compared with the signal (f) to obtain a pulse width signal (j) that the signal (i) is a carrier of the PWM control. The signal (j) is input to a waveform composite circuit 15 to be combined with a 3-phase AC signal C output from a ring counter 7 to become a PWM control signal K. |
