Okay, this situation is complex and concerning. Let's break down the issues and address them one by one.1. The Problem: High Voltage & Incorrect Configuration High Leg Delta Misunderstanding

The initial statement of a 240V high-leg delta system, coupled with the later voltage readings, is confusing. A true high-leg delta system would have: Phase-to-Phase: Around 240V Phase-to-Neutral (two phases): Around 120V Phase-to-Neutral (the high leg): Around 208VThe voltage readings of 133V per leg to neutral, 270V phase-to-phase, and 296V high leg to ground do not match a standard high-leg delta configuration. It is possible the transformer is not properly grounded causing the voltage to drift.

480V Motor Operation at 485V

Operating 460V (or 440V) motors at 485V phase-to-phase is a problem. While some motors have a slight tolerance (+/- 10% is a general guideline), exceeding the rated voltage can lead to:

Increased Magnetizing Current

The motor core will be driven harder, leading to higher core losses and increased heat.

Reduced Motor Life

Insulation breakdown is accelerated at higher voltages. The heat accelerates this process.

Winding Failure

In extreme cases, overvoltage can directly cause winding failure.

Increased Vibration

Magnetic saturation can contribute to increased vibration and noise.

Japanese 200V Motors at 270V

This is a severe problem. Operating a 200V-rated motor at 270V is far outside of any reasonable tolerance. Expect greatly reduced motor life and a high probability of premature failure. The 270V reading indicates the phase to phase supply voltage and this is just as much a problem as the motor windings are not going to be able to handle 270v and will cause premature failure.

Overheating Transformer (115kVA Reverse Wound)

The combination of high voltage and a reverse-wound transformer running hot and loud is a very bad sign.

Reverse Winding Issues

While it's possible to reverse-wind a transformer, it's not ideal. Transformers are designed with specific winding ratios and insulation thicknesses. Running them in reverse can cause inefficiencies and increased losses.

High Voltage Impact

The higher input voltage is exacerbating any design limitations of the reverse-wound transformer.

Overloading (Potential)

The transformer might be overloaded if it's working harder to compensate for the voltage mismatch and the load demand.

Insulation Breakdown

The overheating is likely damaging the insulation within the transformer, leading to eventual failure.

2. Is the Owner Right? No.

The building owner's dismissal of the problem because "it's been that way for years" is extremely short-sighted and negligent. Just because something has been happening doesn't mean it's correct or safe. Continued operation under these conditions will inevitably lead to equipment failures, potentially catastrophic ones, and increased costs in the long run.3. Immediate Actions & Recommendations1. Qualified Electrical Contractor

You need to hire a qualified and experienced electrical contractor immediately. They need to:

Verify the Utility Supply

The contractor needs to contact the utility company and confirm the correct voltage and configuration for the incoming service. The readings you provided suggest a possible utility issue or incorrect transformer tap setting.

Thoroughly Inspect & Test All Transformers

Assess the condition of all transformers, verify their winding ratios, and test their insulation resistance. The reverse-wound transformer needs special attention.

Measure & Document Voltages & Currents

Get accurate readings of phase-to-phase, phase-to-neutral, and current draw on all circuits and equipment.

Inspect Motor Nameplates

Carefully check the voltage ratings on all motors.

Evaluate Wiring and Grounding

Ensure that the electrical system is properly grounded and that wiring is appropriate for the voltage and current.

Check Transformer Taps

Verify that the transformer taps are set correctly to provide the appropriate output voltage.2.

Correct Voltage Problem

The primary goal is to get the voltage to the correct levels (460/480V for the larger motors and 200V, preferably with a proper step-down transformer, for the Japanese motors). Possible solutions include:

Utility Correction

If the utility supply is incorrect, the utility company needs to fix it.

Transformer Replacement/Reconfiguration

If the existing transformers are incorrectly sized or configured, they need to be replaced or reconfigured. This could involve replacing the reverse-wound transformer with a properly sized and configured transformer.

Buck-Boost Transformers

Small voltage corrections can sometimes be achieved with buck-boost transformers. However, this isn't usually the best solution for a large voltage difference.

Autotransformers

Autotransformers can be used to step up or step down voltages efficiently.

Variable Frequency Drives (VFDs)

Consider using VFDs for the motors, especially the Japanese motors. Some VFDs can accept a wider range of input voltages and provide the correct voltage to the motor.3.

Address the Japanese Motors



Replace

The best solution is to replace the 200V motors with properly rated (460/480V) motors.

Dedicated Transformer

If replacing isn't feasible immediately, install a dedicated step-down transformer specifically for the 200V motors.4.

Safety First

Shut down any equipment that is operating dangerously until the voltage issue is resolved. The risk of fire or equipment failure is significant.5.

Document Everything

Keep detailed records of all measurements, inspections, and repairs.

In summary, the high voltage and mismatched equipment are creating a dangerous and costly situation. Ignoring the problem will only lead to more significant problems in the future. The building owner needs to understand the severity of the issue and take immediate action to correct it.Disclaimer: The information provided here is for general guidance only and should not be substituted for the advice of a qualified electrical contractor. Flag for review