How is load calculated on an open transformer bank?

The correct calculation for load on an open transformer bank in a three-phase system utilizes the factor of 0.57. This is based on the relationship between line and phase currents in a three-phase system, particularly for balanced loads.

In a three-phase system, the apparent power (load) can be represented as the product of line voltage and line current. However, when dealing with transformer banks, especially when assessing load across different configurations (open delta, closed delta, etc.), the transformation can lead to a situation where the effective load must be adjusted to determine the actual power being handled. In particular, using the factor of 0.57 allows for the conversion between the line (total) load and the phase load in an open configuration, where not all transformers are fully utilized.

This multiplication factor recognizes that an open transformer bank does not have the same capacity as a fully connected three-phase transformer set, hence reducing the apparent load to accurately reflect the maximum carrying capability while adhering to safety and performance standards within the system.

The approach of using a conversion factor is essential for understanding how to safely and efficiently manage and distribute electrical loads within such configurations.