| 摘要 |
PURPOSE:To measure a load current on a single electric energy meter by extracting the load current from a current transformer through utilizing a period other than a sampling period according to a pulse width modulation system. CONSTITUTION:Switches 5, 6 are turned on and off respectively by a pulse coming from a pulse width modulating unit 1 of an electric energy meter 10 with its width modulated, an output of a current transformer 4 is thus sampled, and an electric energy is measured by a current-frequency converter 7 generating a pulse of frequency proportional to the electric energy from integrating a current. When the switches 5, 6 are kept on and off respectively in a period other than the sampling period, an output current of the current transformer 4 is impressed on a large gain feedback amplifier 12a of a current-voltage converter 12, an input terminal 11a of the amplifier 12a turns standing at an ideal earthing potential, and an influence on the current transformer 4 is thus minimized from connecting the converter 12. According to this constitution, a load current can be measured through a single electric energy meter without providing any special monitor. |
