| 摘要 |
<p>A converter circuit (2) converts an inputted alternating current power (1) to a direct current voltage (Vdc), and an inverter circuit (3) converts the direct current voltage (Vdc) to a three-phase alternating current and drives a synchronous motor (4). A microcomputer (A1) calculates an active power (P) of the synchronous motor on the basis of a power source current (Idc) of the inverter circuit, and estimates an effective current value (Iac) of the inputted alternating current power on the basis of: an effective voltage value (Vac) of the inputted alternating current power, calculated on the basis of a previously measured relationship between the direct current voltage and the active power of the synchronous motor; the active power (P) of the synchronous motor; and the power factor (cos(theta)) of the inputted alternating current power.</p> |
