Which of the following best describes an open delta transformer?

An open delta transformer configuration is characterized by its use of two transformers to create a three-phase system from a lower number of transformers. When only two transformers are used, they are connected in such a way that they can still provide a three-phase output, albeit with some limitations. This configuration is especially useful in situations where the third transformer is not available or when an economical solution is required for three-phase power needs.

An open delta setup allows for continued service in the event of a transformer failure, as it can still operate with reduced capacity. While this might not deliver the full efficiency or capacity of a traditional three-transformer delta connection, it remains a practical solution in certain applications. The terminology "open" reflects that the third corner of the delta is not connected, thus occupying less physical space and investment compared to a full delta arrangement.