1:1 transformers, also known as isolation transformers, are primarily used for galvanic isolation, allowing the separation of circuits while coupling them through magnetic flux. They are essential in applications requiring electrical decoupling, such as in test workbenches to prevent grounding issues during device testing. Additionally, these transformers are utilized in three-phase configurations like Star-Delta to manage zero sequence currents and voltages, particularly in protection relay circuits. They also help eliminate common-mode interference, making them valuable in audio circuits to reduce unwanted noise. Overall, 1:1 transformers play a crucial role in enhancing safety and signal integrity in various high-tech applications.