Good evening, Jonathan. This is a complex situation with a few layers to unpack. Let's break it down, and I'll provide guidance and resources where I can.

First, let's address the high-leg (stinger leg, red leg, wild leg) issue.

You're correct that many motors and sensitive equipment are not designed to handle the imbalanced voltages associated with a high-leg delta system. The 210V phase-to-ground on your B-phase is the problem.

Regarding Rewiring the Rotary Phase Converter



No, you cannot simply rewire the idler motor to eliminate the high leg. A rotary phase converter, by its nature, takes two phases of power and uses a rotating machine (the idler motor) to create a third, somewhat balanced phase. It doesn't inherently address the imbalance coming into the system. The fact that your converter output is still showing a high leg (240V to ground on the generated phase) indicates the converter itself is being fed a system that is unbalanced in reference to ground. This makes sense because the converter cannot "fix" the high-leg from the incoming power.

Your Options & A More Practical Approach

Given the constraints and the cost sensitivity of your customer, let's focus on the most practical solutions. Return the rotary phase converter. It is not going to work. Isolation Transformer is the Most Sensible The best solution, as you're already considering, is to use an isolation transformer specifically designed to convert the high-leg delta to a standard 3-phase, 240V delta (or wye) configuration. How it Works

The transformer essentially isolates the high-leg delta service from the saw's power supply. It takes the incoming high-leg delta and steps it down, while also creating a balanced 3-phase output.

Important Considerations



Transformer Sizing

Crucially, you must size the transformer to handle the inrush current of the saw motor. An undersized transformer will cause voltage drop and can damage the motor. Consult the saw manufacturer for the motor's full load amps (FLA) and locked rotor amps (LRA). A rule of thumb for inrush is 6 times FLA. Your transformer must be able to handle this LRA.

Transformer Taps

Some transformers come with taps that allow you to adjust the output voltage. This can be useful if you need to fine-tune the voltage to match the saw's requirements.

Transformer Grounding

Ensure the transformer is properly grounded according to the NEC (National Electrical Code). This is crucial for safety. You may need to establish a new grounding electrode system at the point of the transformer if one does not currently exist.

Why Other Approaches Are Less Desirable



New Service

You mentioned the customer's reluctance to pay for a new service. While a new service with a proper 3-phase configuration (e.g., 120/208V wye or 240V delta without a high leg) would be the ideal solution, it's often the most expensive.

Transformer Configurations Explained

You asked about transformer configurations. Here's a basic overview, but I highly recommend supplementing this with more in-depth resources (links below). Delta (Δ)

Closed Delta: The three windings are connected in a closed loop, forming a triangle. Advantages include good fault tolerance (if one winding fails, the system can often continue to operate, albeit at reduced capacity). Open Delta: Two windings are used, forming an "open" triangle. This is less expensive than a closed delta, but it has reduced capacity and less fault tolerance. Grounded Delta: One corner of the delta is grounded. This provides a ground reference and can help limit voltage to ground during faults. The high-leg system is a specific case of a grounded delta. Ungrounded Delta: No corner of the delta is grounded. This offers some advantages in terms of fault tolerance, but it can be problematic in terms of overvoltages during ground faults.

Wye (Y)

Wye (Star): The three windings are connected to a common neutral point. This is the most common configuration for distributing 120/208V power. It provides both phase-to-phase (208V) and phase-to-neutral (120V) voltages. Open Wye: Less common, similar to open delta in terms of reduced capacity.

Isolation Transformer

This is not a specific winding configuration. It's a function. An isolation transformer isolates the primary (input) side from the secondary (output) side. This is done to provide electrical isolation, block DC currents, and change voltage levels (step up or step down). They can be configured in delta or wye on either side. The key is that they provide a new neutral reference and can balance unbalanced systems.

Resources for Learning More Mike Holt Enterprises

Mike Holt is a well-respected electrical trainer. His website and books are excellent resources. (Google "Mike Holt Transformers")

Eaton's Transformer Handbook

Eaton (a major electrical equipment manufacturer) provides a free, comprehensive transformer handbook. (Google "Eaton Transformer Handbook")

Your Local IBEW or IEC Training Center

If you have access to union or industry training centers, consider taking a refresher course on transformers and 3-phase systems. Hands-on experience is invaluable.

Recommendations


Return the rotary phase converter. It will not solve your problem.2. Consult with a qualified electrical engineer. This is the best course of action. An engineer can properly assess the site, calculate the load requirements, select the correct transformer, and ensure compliance with all applicable codes. This will minimize risk and ensure a safe and reliable installation.3. If you proceed without an engineer, be extremely careful. Research

Thoroughly research transformers and 3-phase systems.

Sizing

Over-size the transformer to account for inrush current.

Grounding

Implement a proper grounding system.*

Inspection: Have your work inspected by a qualified electrical inspector.I hope this comprehensive response is helpful. Please let me know if you have any further questions. Safety is paramount, and I strongly encourage you to seek professional guidance on this project. Good luck! Flag for review