| 摘要 |
The invention relates to an electronic power meter including a current- sensing transformer (12) capable of sensing widely varying values of current and comprising primary windings (38, 39) for direct connection to the current component of an electric energy quantity to be measured. A secondary winding (41) is inductively coupled to the primary windings to produce an analog signal (ei) that is proportional to the time derivative of the current component. The transformer may have a magnetic core (40) with a cap which can be bridged by saturable shunt plates (76), Figure 3 (not shown) to give linearity at low current levels : or a pick-up coil (97), Figure 4 (not shown) can be positioned near the gap to respond to stray flux and give a signal that is summed with the secondary output. Alternatively, the secondary may be a toroidal coil around the line conductor, Figures 6-8 (not shown). The transformer responds to currents from 1 DIVIDED 2A to 200A to provide a suitable signal for the high impedance input of the measuring circuitry (43). <IMAGE> |
