Your idea is interesting, and it's good you're thinking creatively! However, what you've drawn WILL NOT WORK as intended and is a very bad idea for several reasons. It's dangerous and could result in significant damage to equipment and potential hazards.Here's a breakdown of why and what you should consider instead

Why Your Proposed Transformer Setup is Problematic:

1. Phase Imbalance and Overloading

You're essentially trying to force a balanced 3-phase system from a severely unbalanced source. Each transformer would be burdened with a different load, especially since each leg of the single-phase input is 120 degrees apart. You're essentially creating a very imbalanced load on your single-phase feed. The single phase feed's imbalance would then be amplified. This will also likely make it very difficult to reliably supply power to the three phase load as the voltage and current would be very unstable.2.

Phase Shift Issues

While you're thinking about the 120-degree phase difference at the source, transformers don't magically create phase shifts in the way you're hoping. A standard transformer provides the same phase shift in its secondary voltage as it has in its primary voltage.3.

Voltage Issues

You are putting 120v across the input to each transformer. The output of each transformer would be about 120v. To get 208v across the 3-phase load you would need the voltage between any two phases to be 208v. Connecting the transformer outputs as shown would only supply 120v to the load between any two of the three phases.4.

Potential for Transformer Saturation and Damage

Unbalanced loading can lead to transformer saturation and overheating, especially with the proposed delta connection.5.

Safety Concerns

This setup is inherently unsafe due to the unbalanced loads, potential for high circulating currents, and the possibility of creating dangerous voltage imbalances. It could lead to equipment failure, fire, and electrocution hazards.6.

Lack of Isolation

Your diagram shows the neutral connected throughout the circuit, which can create problems with ground loops and potential hazards.

Better Alternatives (Ordered by Preference)

1.

The Right Solution: Cost Justification & Power Upgrade

This is, by far, the correct solution. You need to:

Thoroughly Cost Out the 3-Phase Upgrade

Get a detailed quote from a qualified electrical contractor for running a proper 3-phase service to the building. Include everything: Permits, trenching, conduit, wire, transformers (if needed), panel upgrades, labor, etc.

Quantify the Benefits of 3-Phase

The benefits often outweigh the initial cost. Consider: Improved efficiency and lifespan of the machine. Potential for future expansion and other 3-phase equipment. Reduced wear and tear on the existing single-phase system.

Present a Comprehensive Cost-Benefit Analysis

Convince management that the long-term benefits of a proper 3-phase service justify the investment. Explain that you'll get it done right, and there are no potential issues that may cause more problems down the road.2.

Rotary Phase Converter

A rotary phase converter (RPC) is a single-phase to 3-phase conversion device that uses a motor generator set. These are commonly used for this exact reason. These are usually reasonably efficient and the phase balance is better than a static phase converter.3.

Static Phase Converter

A static phase converter (SPC) is a type of phase converter that uses capacitors and inductors to create a simulated 3-phase output from a single-phase input. SPCs are less expensive than rotary phase converters but are also less efficient and provide a less balanced 3-phase output.4.

Variable Frequency Drive (VFD) with Single-Phase Input

Some larger VFDs are designed to accept single-phase input and output 3-phase power to a motor. However, this only works if the load is a motor. If the machine has other 3-phase components, this won't work.

Important Considerations for Any Solution



Code Compliance

Any electrical work must comply with local electrical codes and regulations. Get permits and inspections.

Qualified Electrician

All electrical work must be performed by a licensed and qualified electrician.*

Machine Requirements

Carefully check the machine's nameplate for its exact voltage, current, and power requirements. Select a conversion method that can reliably meet those needs.

In summary, your proposed transformer configuration is dangerous and won't work. Focus on getting a proper 3-phase service or exploring a phase converter solution. Safety and code compliance are paramount. Flag for review