A Brief Outline of Motor Rewinds

Electric Motor Rewind


One of the most common faults with pumps are the electric motors that drive them burn out.


If an electric motor burns out the solution for the repair would be a replacement motor as this would be the most effective and quickest way. However, some old motors have special shafts and cannot be replaced so easily, therefore a rewind can be carried out to get it back working.


Rewinding motors is a very specialized skill. The correct terminology of rewinding is Armature winding. Most motor Rewinders use the existing windings to gather the data to rewind the motor. Information such as connections, turns on each coil and copper size is recorded.



  • Stator- Stator is the term used for the frame in which winding are held in (i.e. the Stationary part of the motor).
  • Windings- winding is the term used for the copper wire that is wound inside the spool.

There are many different reasons as to why motors burn out, such as dead short to earth, short between phases, a complete burn out and more. Whatever the reason is that your motor has burnt out, the below should outline some of the steps you need to take to rewind it if necessary.


The inside of the stator has a spool, and this is made up of various pre-fabricated laminations which are stacked and welded together. The laminations have grooves machined in them which are insulated with a very high temperature material call Nomex. 


The copper wire is normally pre dipped in a protective coating and comes delivered on a bobbing. Each motor is different to another depending on kW size, voltage, current, speed and many other factors. The copper wire is wound on a machine in a certain shape which is made up groups of coils. Each coil has a certain amount of turns and different wire sizes (gauge).


Once the coils have been wound in groups, they would then be manually installed inside the insulated slots on the spool. Each set of coils are independently insulated from each other to prevent any electrical shorts. Each motor has different number of coils and slots depending on the motors performances.


Once all of the coils have been installed, the next stage would be to connect the copper ends to leads. Again, each motor is connected differently depending on its performance. When the connections are formed they are braised together. What this ensures is that the connection is good and will not result in a high resistant joint, which ultimately could blow a hole in the newly wound coils.


The final process of rewinding would be varnishing the newly wound coils. The stator would be dipped in a specialized varnish; this would create a seal on the copper which would act as a protection. In some large stators they would need to be vacuum varnished as this would insure full dispersion of the varnish in every air gap possible. The stator would then be put in an induction oven that would reach temperatures of around 200 degrees. This process sets the varnish so it is hard and secure. It would take around 6-8 hours depending on the size of the stator for this to cure.


The motor would then have to be rebuilt and preliminary tests would need be carried out.


If you would like a quote for us to rewind or replace your pump's motor, please contact us on 01322 292 415 or fill out our form here.