Your drawing is insightful, and you are right on track with your thinking! Let's break down what's happening and address your questions

Analysis of Your Drawing

Your drawing accurately depicts a configuration of three single-phase transformers used to derive 120/240V single-phase power from a three-phase source. This method aims to balance the load across the three phases of the generator. Here's a breakdown: Three Single-Phase Transformers

The key is that each transformer is dedicated to one phase of the 480V three-phase supply. Each transformer steps down 480V to 120/240V.

Balanced Loading (The Goal)

By connecting the 120/240V loads across all three transformers, the goal is to draw current relatively evenly from each phase of the generator. This is crucial to avoid the load imbalance tripping you experienced with the previous attempt.

Neutral Connection

The critical point is the connection of the 'X2' terminals of all three transformers. This point forms the neutral for the 120/240V single-phase output. It's the center tap of each secondary tied together.

Voltage Relationships

The resulting 120/240V single-phase power is then distributed to the loads.

How This Works


Phase-Specific Transformation

Each transformer operates independently, stepping down the voltage from one phase of the 480V source.2.

Load Distribution

The 120/240V loads are distributed across the outputs of the three transformers. Ideally, you want to balance the loads connected to each transformer as much as possible.3.

Current Balancing (Ideal)

If the load is perfectly balanced (equal load on each transformer's output), the current drawn from each phase of the 480V generator is also balanced. In reality, perfect balance is difficult to achieve, but the system aims to get close enough to avoid overloads.4.

Neutral as a Reference

The common neutral point ('X2' connection) provides a stable voltage reference for both the 120V and 240V circuits.

Answers to Your Questions Does my attached drawing look right? Yes, your drawing accurately represents the described setup. The critical part is the tieing together of the neutral (x2) And btw, how does this work ??? Answered above EDIT: And can this be done with a single poly-transformer instead of 3 separate ones?

Yes, absolutely! You're thinking in the right direction. A three-phase to single-phase transformer (often a "Zig-Zag" or "Interconnected Star" transformer, or a "Scott-T" transformer) is specifically designed for this purpose. Zig-Zag transformers are particularly good at balancing loads when converting three-phase to single-phase. They are specifically designed to mitigate neutral current problems and distribute load more evenly across the three phases. Scott-T transformers can convert three-phase power to two-phase power, which can then be combined to create single-phase power. This approach can be more efficient than using three separate single-phase transformers, but the wiring and design are more complex. A 2 phase setup is better than a single leg load.

Advantages of a Poly-Transformer (vs. Three Separate)



Efficiency

A well-designed poly-transformer is generally more efficient than using three separate transformers.

Cost

Typically, a single poly-transformer will be more cost-effective than three individual units.

Space Savings

A single unit takes up significantly less space.

Wiring Simplification

Wiring is cleaner and less complex with a single transformer.*

Improved Balancing

The internal design of the transformer inherently helps to balance the load across the three phases.

Recommendations1. Verify Connections

Double-check all wiring connections, especially the neutral point, to ensure proper grounding and avoid any potential short circuits or voltage imbalances.2.

Load Balancing

Attempt to balance the load as much as possible when distributing power to the various appliances or equipment.3.

Consider a Poly-Transformer

I strongly recommend replacing the three single-phase transformers with a single three-phase to single-phase transformer (Zig-Zag type). It will provide a more efficient, reliable, and cost-effective solution. In your quote, provide the cost of the single Zig-Zag type and the time involved to make the change. It should sell itself.4.

Calculate Transformer Size: Ensure that the single transformer you select is adequately sized to handle the total load requirements. Factor in a safety margin to allow for future expansion. The 65kw generator output should provide a guide.Let me know if you would like to dive deeper into Zig-Zag transformers, Scott-T transformers, or any other aspect of this project. Flag for review