| 摘要 |
PURPOSE:To detect secondary currents with the high precision of detection by obtaining input power from the instantaneous values of the detecting values of the primary voltage and primary currents of a motor, deviding the input power by the amplitude of primary voltage and detecting secondary currents. CONSTITUTION:Currents detected by current detectors 3, 4 are converted into two-phase currents ialpha', ibeta by a phase converter 6. On the other hand, voltage detected by a voltage detector 5 is converted into two-phase voltage Valpha', Vbeta by a phase converter 7. A primary input P1 to a motor is obtained by multipliers 8, 9 and an adder 12. The primary-voltage amplitude value ¦V1¦ of the motor is acquired by multipliers 10, 11, an adder 15 and a switch 16. Power P' is devided by the primary-voltage amplitude value ¦V1 as an output from the switch 16 by using a divider 17, and increased by L/M times by an amplifier 18 and secondary currents i2 are obtained. Where M represents exciting inductance and L=M+l (l represents leakage inductance) holds. |
