Motor Rewinding: What It Is and When to Rewind Instead of Replace

What is motor rewinding?

Motor rewinding is the repair of an electric motor by replacing its windings, the copper wire coils that turn electrical power into a magnetic force. When a motor's windings burn out, rewinding removes the old wire, fits new wire to the original specification, and brings the motor back into working order. It restores a motor that would otherwise be scrap, instead of replacing the whole unit.

For an industrial motor, rewinding is often the difference between a repair bill and buying a new machine. The question is usually not whether a motor can be rewound, but whether rewinding is the better choice for that motor.

Why windings fail

The windings sit in the stationary part of the motor, the stator, and are wrapped in insulation. Over time or under stress that insulation breaks down, which lets the coils short out and burn. Common causes include:

• Overload, where the motor is worked harder than it is rated for and overheats.
• Overheating from poor cooling, a blocked fan or a hot environment.
• Moisture and contamination, which attack the insulation.
• Electrical problems, such as voltage imbalance or frequent heavy starts.
• Age, as insulation slowly hardens and weakens over many years of service.

If the motor trips, stalls or stops, and there is a burnt smell, the windings have probably burnt out.

What the rewinding process involves

Rewinding is skilled work carried out in a workshop, not a job for the field. In simple terms it follows these steps:

• Assess the motor and record the original wires and winding details, so the new winding matches the old.
• Strip out the old winding and clean the stator core.
• Fit new wire and insulation, wound to the recorded specification.
• Connect and secure the new coils.
• Test the rewound motor before it goes back into service.

Done properly, a rewound motor performs as it did before the winding failed, and it holds its original efficiency. Done poorly, a rewind can leave the motor running hotter and drawing more power, which is why the skill of the workshop matters. The key is matching the new winding to the original so the motor keeps its correct characteristics.

When to rewind and when to replace

Rewinding is not the answer for every motor. The choice comes down to the size and type of motor, the condition of its core, and cost.

As a rule, the larger or more specialised the motor, the more sense it makes to rewind rather than replace it, provided the core itself is sound. Smaller standard motors are often simply swapped for a new one, because a new motor costs little more than the labour to rewind an old one.

Does rewinding or replacing cost less?

Cost is usually the deciding factor once the motor has been assessed. A common industry rule of thumb is that if a rewind would cost more than roughly half to two-thirds the price of an equivalent new motor, replacement is the better value. Below that, rewinding is normally cheaper, and for large or hard-to-source motors it is far cheaper than buying new.

Two things push the sums toward rewinding: a large motor, where a new unit is expensive, and a specialised or long-lead motor that is not quick to replace. Two things push toward replacing: a small standard motor, where new is cheap, and a damaged core, where the repair is no longer a straightforward rewind. A workshop can give a clear recommendation once it has opened up and assessed the motor.

Motor rewinding and gear motors

The motor in a gear motor can fail in the same way as any other electric motor, and it can be rewound in the same way. Because a gear motor pairs a motor with a matched gearbox, restoring the motor by rewinding keeps the whole unit in service rather than replacing an assembly that is otherwise sound. That matters most when the gearbox is fine and only the motor has burned out. It is also worth noting that standard motors might not fit all gearboxes, and it might make more sense to rewind the existing motor.

AVM offers motor rewinding as a service, so a failed winding does not have to mean the end of the motor. To learn more about the geared motors AVM supplies and services, visit the geared motor category.

Getting the most from a rewound motor

A rewound motor lasts best when the reason the winding failed is understood and put right. If the motor burned out from overload, running it the same way will shorten the life of the new winding too. Before a rewound motor goes back to work, check that it is correctly rated for its job, that its cooling is clear and unblocked, and that the electrical supply feeding it is sound. Done this way, a rewind gives the motor years of further service.

Frequently asked questions

What is motor rewinding?

It is the repair of an electric motor by replacing its burnt-out windings with new wire wound to the original specification, bringing the motor back into service instead of scrapping it.

Why do motor windings burn out?

Usually because the insulation around the coils breaks down, from overload, overheating, moisture, electrical faults or age, which lets the windings short and burn.

Is it better to rewind or replace a motor?

Larger, powerful or specialised motors with a sound core are usually worth rewinding. Small, standard motors are often replaced. The condition of the core and the cost of a new motor are the deciding factors.

How much does it cost to rewind a motor?

It depends on the size and type of motor, but a common guideline is that rewinding is worthwhile when it costs less than about half to two-thirds the price of a new motor. For large or specialised motors, a rewind is normally well below that.

Does AVM offer motor rewinding?

Yes. AVM rewinds electric motors, including the motors used in gear motors, restoring the winding rather than replacing the whole unit.

Will a rewound motor fail again?

Over time, any equipment will fail. However, if the reason for the motor coil burn out is fixed, the motor can last a few more years rather than just months.