Final answer:
To connect single-phase transformers to form a three-phase bank, the voltage rating, positions of tapes or dual-voltage switches, percent impedance, and KVA rating must be similar or identical.
Step-by-step explanation:
In order to connect single-phase transformers together to form a three-phase bank, all of the following must be similar or identical: a) voltage rating, b) positions of tapes or dual-voltage switches, c) percent impedance, and d) KVA rating.
When connecting transformers in a three-phase configuration, it is important that all transformers have the same voltage rating to ensure proper synchronization of the phases. Additionally, the positions of taps or switches should be the same to ensure consistency in voltage regulation.
Furthermore, the percent impedance should be similar to ensure balanced loading and protection against fault currents. Lastly, the transformers should have the same KVA rating to ensure equal power distribution among the phases.