Which two current values are important when working with transformer connections?

When working with transformer connections, phase current and line current are critical values to consider because they relate to how the transformer transforms electrical energy between different voltages. In three-phase systems, understanding the relationship between phase current and line current is essential for proper transformer sizing and ensuring that the system operates within safe limits.

Phase current refers to the current flowing in each individual winding of the transformer, while line current is the current that flows in the external lines connecting the transformer to the load. The relationship between these two currents depends on the type of transformer connection (e.g., delta vs. wye) being used. This information is vital for calculating load requirements and for designing circuits correctly to avoid overloads and ensure efficient operation.

In contrast, while other values like voltage and frequency or line voltage and phase voltage are important, they do not directly pertain to the current characteristics that are crucial in transformer operations. Current and power, although related, do not address the specific roles of phase and line currents in connection configurations.