| 摘要 |
<p>Electric power is equivalent to the product of voltage and current in a power circuit. The present invention employs, as a multiplier to obtain the product of a voltage and a current, a pulse-width modulator which consists of an integrator, a comparator having a hysteresis characteristic connected to the output side of the integrator, and a feedback circuit for feeding the output of the comparator back to the input side of the integrator. The voltage of the power circuit is applied to the pulse-width modulator of such a circuit configuration so as to be pulse-width modulated, and the output of the modulator serves to intermittently turn on or off an analog switch to which the current of the power circuit is applied, thereby multiplying the voltage by the current. The integrator, comparator and feedback circuit constituting the pulse-width modulator and also the analog switch are composed entirely of electronic circuits, and the inputs of both the pulse-width modulator and the analog switch are equipped with a protective circuit against an impulse input. For conversion of a single-phase power to a d-c signal, one pulse-width modulator and one analog switch are employed as described above; and for measurement of three-phase power, three-phase reactive power or three-phase four-wire power, two pulse-width modulators and two analog switches of the same composition are employed.</p> |
