What connection is required on the low side of the transformer bank for a service rated at 240/480 3-phase 4-wire?

In a service rated at 240/480 volts three-phase four-wire, the low side of the transformer bank should be connected in a Wye configuration. This is because a Wye connection provides a neutral point, which is essential for a four-wire system.

The neutral allows for the distribution of 120 volts (which is half of 240 volts) for single-phase loads while also accommodating three-phase loads. This connection facilitates balanced loading across the three phases, which is crucial for maintaining system stability and efficiency.

Moreover, with the Wye configuration, it allows for the generation of multiple voltage levels from a single transformer bank. In this specific setup, it can provide both the higher line-to-line voltage (480 volts) and the lower phase-to-neutral voltage (240 volts), fulfilling the operational requirements of various electrical appliances and equipment in a commercial or industrial setting.

Choosing an alternative connection like Delta would not accommodate the neutral requirement effectively in this case, and Zigzag connections are typically used for grounding purposes, not for serving standard loads. Star is another name for Wye, and could potentially be considered correct in different terminologies, but in this context, Wye is the most appropriate term.