What is the relationship between phase current and line current in transformer connections?

The concept of phase current versus line current is crucial in understanding transformer connections, particularly in three-phase systems. When we discuss a transformer with a wye (Y) or delta (Δ) connection, the relationship between line current and phase current differs.

In a delta connection, the line current is indeed greater than the phase current. This is due to the configuration of how the phases are wired. In a delta setup, each line current feeds two phases, causing the line current to equal the square root of three times the phase current. Hence, this configuration results in a situation where the line current is effectively higher due to the geometric properties of current distribution in this type of connection.

On the other hand, in a wye connection, the phase current and line current are equal. Therefore, the specific configuration of the transformer—whether it's delta or wye—determines this relationship. This is why the relationship is sometimes referred to as dependent on the transformer type, but specifically for a delta connection, the line current is indeed greater than the phase current.

Understanding these concepts is integral to working with transformers in various applications, particularly in power distribution and system design.