What is the bank capacity percentage of total nameplate capacity in an open wye-open wye bank?

The correct answer is 75%. In an open wye-open wye bank, the effective capacity or bank capacity percentage is determined by the configuration of the transformers within the bank. The nameplate capacity refers to the maximum capacity the transformers can handle, while the bank capacity percentage indicates how much of that capacity is actually available for use in this specific configuration.

When transformers are set up in an open wye-open wye configuration, they do not share load evenly across all phases, as opposed to other configurations which may allow for better balancing of loads. This leads to a 25% reduction in effective capacity when compared to the total nameplate capacity. Consequently, the bank capacity percentage that can be effectively utilized becomes 75% of the total nameplate capacity.

Understanding these transformer configurations and their impacts on capacity utilization is crucial for properly sizing equipment and ensuring efficient operation in electrical systems.