What is a typical excitation-current test data pattern for a three-legged core transformer?

In a typical excitation-current test for a three-legged core transformer, the expected current data pattern would show two similar current readings and one lower current reading. This occurs because of the design and configuration of three-legged core transformers, which are built with a central leg and two outer legs.

During the excitation-current test, the two outer legs generally experience similar magnetic paths, leading to their excitation currents being almost equal. The central leg, however, may have slightly different characteristics due to its unique placement and magnetic flux distribution, often resulting in a lower current reading compared to the other two legs. This pattern indicates that the transformer is functioning correctly, with balanced magnetization for the outer legs while also accounting for the different magnetic properties of the central leg.

This outcome reflects the functional design of three-legged core transformers and is critical for determining their operational efficiency and verifying their integrity during testing.