Excitation tests can be made on both C and T class current transformers to permit comparison with published or
previously measured data to determine if deviations are present.
Before the excitation test is made, the current transformer should be demagnetized as described in 4.3.
To perform the test, an ac test voltage is applied to the secondary winding with the primary open circuited as shown in
Fig 9. The voltage applied to the secondary of the current transformer is varied, and the current drawn by the winding
at each selected value of voltage is recorded. Readings near the knee of the excitation curve are especially important
in plotting a comparison curve. For current transformers with taps, the secondary tap should be selected to assure that
the current transformer can be saturated with the test equipment available. The highest tap which can accommodate
that requirement should be used.