This is a good question with a few layers to it. Here's a breakdown of my thought process and considerations, along with my eventual recommendation

Understanding the Constraints and Goals
EV Charger Requirement

Absolutely must be 240V, single-phase. No flexibility here.

No Neutral/120V Needed

This simplifies things considerably. We don't need to derive a neutral for other loads.

LED Lighting Flexibility

The LED lights can run on anything from 120V to 277V. This gives us freedom.

Primary Service

Utility delivers at high voltage. We're responsible for the transformer.

Efficiency & Voltage Drop

Minimize losses and voltage drop are important goals.

Future Expansion

Consider future scalability. Adding more chargers later should be relatively easy.

Cost

While not explicitly stated, cost is always a factor.

Analyzing Possible Transformer Configurations

Here's a look at the likely options. I'm assuming the utility will let you choose from a reasonable range of primary voltages.1. Single-Phase Transformer (High Voltage to 240V)

Pros: Simplest, potentially lowest cost initial transformer. Best for a single phase charger. Cons: Load imbalance on the primary side if not perfectly distributed across all three phases by the utility, potentially greater voltage drop compared to a balanced 3-phase system. Limited scalability if the site is expanded significantly.2.

Three-Phase Transformer (High Voltage to 240V Delta)

Pros: Provides three-phase power, even if only using two legs for the chargers. Good choice if you anticipate needing three-phase power later. Cons: Delta systems can have higher circulating currents and voltage imbalances if not loaded evenly. Delta systems are more prone to producing harmonics.3.

Three-Phase Transformer (High Voltage to 208Y/120V, then Step-Up Transformers to 240V)

Pros: Allows for standard electrical equipment to be used. Cons: Highly inefficient since it has two voltage transformations occurring.4.

Three-Phase Transformer (High Voltage to 480Y/277V, then Step-Down Transformers to 240V)

Pros: Allows for standard electrical equipment to be used. Cons: Highly inefficient since it has two voltage transformations occurring.5.

Three-Phase Transformer (High Voltage to 240V Wye)

Pros: Potential for better voltage balance compared to single-phase or Delta. Provides a neutral for future flexibility, even if not currently used. Might be more efficient than Delta, particularly with modern designs. Cons: More expensive than a single-phase transformer initially. Requires careful consideration of neutral grounding and handling even if not used immediately.

Addressing the "No Neutral" Claim

While the chargers themselves don't need a neutral, having a neutral available in the system can be beneficial for a few reasons: Future Flexibility

Needs change. You might want to add other equipment later that does require 120V or 277V (even outlets for maintenance).

Grounding System

The neutral is part of the grounding system. Even if you don't directly use it, a solidly grounded wye system can provide a more stable and safer ground fault path.

Key Considerations for 240V Wye High Leg Delta Alternative: This option generates 240V single-phase, however it includes a 208v "high leg" to ground, which creates safety and incompatibility issues. Grounding

Properly grounding the wye neutral is essential. This ensures a low-impedance path for fault currents. Consult with a qualified electrical engineer on the best grounding method for your site.

Neutral Conductor Sizing

Even if you're not using the neutral for load, it must be sized to carry potential fault currents. Your local codes will dictate the requirements.

Harmonics

EV chargers can generate harmonics. A wye system can help mitigate these, but you'll need to carefully consider transformer derating and potentially add harmonic filtering if the charger load is significant. Talk to your charger manufacturer about harmonic distortion levels.

Recommendation

Given the constraints and goals, my recommendation is a Three-Phase Transformer (High Voltage to 240V Wye). It offers the best balance of efficiency, voltage stability, and future flexibility. The cost difference compared to a single-phase transformer is likely small enough to justify the added benefits. The neutral, even if not immediately used, provides a path to ground and allows for future expansion.

Next Steps1. Consult with an Electrical Engineer

This is not a DIY project. Engage a qualified electrical engineer to perform load calculations, voltage drop studies, and determine the optimal transformer size and configuration.2.

Coordinate with the Utility

Discuss your plans with the utility. They may have specific requirements or recommendations for the transformer configuration.3.

Consider Future Growth

Plan for the possibility of adding more EV chargers in the future. Oversizing the transformer slightly now can save you significant costs later.4.

Investigate Charger Specs

Get detailed specifications from the EV charger manufacturer, including harmonic distortion levels and grounding requirements.5.

Price Out Options

Get quotes for both single-phase and three-phase transformers to compare costs.6.

Prioritize Safety: Ensure that all work is performed by licensed electricians and that the installation meets all applicable electrical codes.In summary, while a single-phase transformer might seem like the cheapest and simplest option initially, the long-term benefits of a three-phase 240V Wye transformer outweigh the slightly higher upfront cost. It provides better voltage stability, allows for future expansion, and offers improved grounding and harmonic mitigation. Most importantly, consult with a qualified engineer to ensure the installation is safe and meets all applicable codes. Flag for review