| 摘要 |
PURPOSE:To obtain the marginal commutation angle as minimum required limit by comparing a cosine signal which coincides in phase with the induced voltage of a synchronous motor and is constant in amplitude with a phase control signal given by the prescribed function to obtain a control leading angle. CONSTITUTION:An induced voltage calculator 14 outputs the induced voltage of arbitrary phase on the basis of armature voltage and current. An absolute value calculator 15 obtains the DC amount of the induced voltage, the induced voltage is divided by a divider 18a by the DC amount, and cosine signal which coincides in phase with the induced voltage of the motor and is constant in amplitude is outputted as a reference signal. On the other hand, in a divider 18b, the DC amount is divided by the detection signal from a rotating speed detector 13 to obtain a magnetic flux. The magnetic flux is divided by a divider 18c by the intermediate DC current to obtain a phase control signal. The control signal is compared by a comparator 16 with the reference signal, and the firing pulse is outputted by a pulse generator 17 at the coincidence time point. |
