Inside the Shop: Rewinding a 600 HP Hermetic Motor

Rewinding a 600 HP hermetic motor isn’t just another job, it’s a complex and technical process that demands the right tools, materials, and most importantly, expertise. When this motor came into our Industrial Division, our team was ready to handle it from start to finish.

Hermetic motors are built to run inside refrigeration and air conditioning systems, sealed within the compressor and immersed in refrigerant. Their tough environment demands precision at every step of the repair, especially winding and insulation, since even a small error can cause serious performance issues or system failure.

What Is Motor Rewinding?

Motor rewinding is the process of replacing the electrical windings in a motor’s stator. Over time, these windings can break down due to heat, moisture, contamination, overload, or just normal wear and tear. A successful rewind restores the motor to its original (or sometimes improved) performance.

The rewinding process generally includes:

• Initial inspection and testing to determine the root cause of failure
• Burn-off or stripping of the old winding using a controlled oven
• Cleaning the stator core and prepping for re-insulation
• Rewinding the coils using the correct wire gauge, turns, and insulation material
• Varnishing and baking to seal the windings and provide mechanical integrity
• Reassembly and testing to ensure the motor performs as expected

In the case of this 600 HP hermetic motor, it required wire, varnish, and winding techniques specific to high-horsepower refrigeration motors. It also required the steady, expert hands of our Industrial Rewind Technician, Tony Virgilio, who is pictured here carefully winding the core.

Once the winding is complete, the motor is reinserted into the compressor casing (pictured in our burn-off oven). It then moves through a final round of cleaning, painting, reassembly, and performance testing to ensure it’s ready to return to service.

Why Rewind Instead of Replace?

Rewinding can be a cost-effective alternative to replacement, especially for large, custom, or OEM motors that may have long lead times or discontinued models. A properly rewound motor can deliver performance equal to or better than its original specs when handled by a trusted repair partner.

At EMR, our Industrial Division combines decades of experience with modern techniques and testing capabilities to get critical equipment like this back in action—safely, reliably, and efficiently.