| 摘要 |
The dynamic range of a current transformer (CT) (17) is increased without reducing the scaling of measurements at the low end of the dynamic range by designing the core (19) of the CT (17) to saturate only after about 90 electrical degrees of the maximum current to be measured. The measurements taken during this first 90 electrical degrees before the core saturates are doubled to in effect add measurements representing the mirror image of the first 90 electrical degrees. Timing of the digitized samples taken during the first 90 electrical degrees is adjusted to account for core reset energy errors, by determining the rate of change of current just after a zero crossing and selecting an empirically determined value of current for timing the start of the measurement samples. <IMAGE> |
