3rd Year Lineman Apprentice Practice Exam

A transformer rated at 7620/13200Y-120/240 is designed to interface with a three-phase system, and its rating indicates that it can be connected in a specific configuration suited for the source voltage. In this case, connecting the transformer to a 7620-volt three-phase three-wire system requires a Delta configuration.

The Delta configuration is commonly used for three-phase systems when the line voltage equals the transformer voltage. In this setup, each phase of the transformer is connected to a phase of the incoming supply, creating a closed loop that allows for continuous flow of current. This configuration provides a balanced load and is particularly effective for heavier loads.

Using a Delta connection in this scenario allows the transformer to effectively handle the phase to phase voltages provided by the 7620-volt system. In contrast, a Wye configuration would not be appropriate as it is typically used for different voltage applications and would not maintain the necessary voltage levels in a three-wire system.

The terms "Parallel" and "Series" are not applicable in this context, as they refer to connections typically found in single-phase circuits or specific load configurations rather than in three-phase transformer operations.