For transformers banked in the line-to-line delta configuration, how must the voltage rating of the transformers relate to the supply circuit?

In a line-to-line delta configuration for transformers, the voltage rating of the transformers must be equal to the supply circuit voltage to ensure proper operation.

When transformers are connected in a delta configuration, they are designed to handle the line-to-line voltage directly. In this configuration, each transformer's primary winding is linked such that it receives the full line-to-line voltage from the supply. Therefore, if the transformer voltage rating is lower than the supply voltage, it may lead to insulation breakdown or overheating, risking damage to the transformer and potentially causing system failures. Conversely, if the voltage rating is higher than necessary, it could lead to inefficiencies without necessarily causing problems, but does not align with optimal design principles, which dictate that the transformer voltage rating should match the supply.

As such, having the transformer voltage rating equal to the supply circuit voltage ensures that the transformers operate effectively within their designed parameters, maintaining system safety and reliability.