| 摘要 |
PROBLEM TO BE SOLVED: To provide a synchronous motor drive capable of calculation of active power and estimation of an input AC current with high precision in a simple configuration.SOLUTION: A converter circuit (3) converts input AC power (1) into a DC voltage (Vdc) and an inverter circuit (3) converts a DC voltage (Vdc) into a three-phase AC current to drive a synchronous motor (4). A microcomputer (A1) calculates active power (P) of the synchronous motor on the basis of a power current (Idc) of the inverter circuit and estimates a current effective value (Iac) of input AC power on the basis of a voltage effective value (Vac) of input AC power, the active power (P) of the synchronous motor and a power factor (cos(&thetas;)) of the input AC power, calculated based on a relationship between the previously measured active power and the DC voltage of the synchronous motor. |
