If you are using the ACTL-1250 series current transformers with a WattNode meter, you may disregard this section because the ACTL-1250 CTs have been optimized for the standard 23kΩ loading of a WattNode meter. For anything other than a WattNode meter, the meter’s input impedance may affect the gain of the CT, because the meter’s input impedance appears as an output load to the current transformer.
The ACTL-1250 series current transformers are designed with an expected output loading: 23kΩ for all models except Opt 1V; the expected loading is 1.0MΩ for Opt 1V models. Different actual loadings will cause small shifts in the gain. A higher load than expected will result in higher gain, while a lower load will result in a lower gain. The phase angle error is not materially affected by the loading.
For all models except Opt 1V, the worst-case effect of different loads follow:
•1.0MΩ load: gain will be high by 0.06% or less
•10kΩ load: gain will be low by 0.13% for ACTL-1250-150, low by 0.08% or less for other models.
To precisely compute the effect of non-standard output loadings, use the following.