Holes in electric motor windings?

These holes are meant to be here though.


This feature in an electric motor winding is unusual but not uncommon. They are there to serve a purpose. This type of motor is used in electric vehicle propulsion. It is the guts of a BAE Systems Hybridrive TB08 electric traction motor.

All electric motors need to be cooled and most standard motors use an airflow across the case. In this motor though the cooling is a liquid cooling system inside the motor itself. The hollow conductors allow the coolant to pass through the windings and then out through the smaller drain-holes. The system then passes over a heat exchanger external to the motor and it is then recirculated.

We've seen hollow conductors in larger motors in the MW range and also large power transmission transformers, yet this is the only type of motor this size that I've seen them on.

For scale the core of this motor stator is around 250mm and the length is around 400mm. Not a large stator by any means however the power the motor can produce at peak performance is 230kW. Quite an output for a motor of this size and no doubt the reason for the cooling system. There will certainly be some heat to be got rid of.

LinkedIn post

This is your call to action 

Electric vehicle motor rewinds and refurbishments are part of what we do at Fletcher Moorland.

Motors from BAE Systems, Siemens ELFA and Volvo are just some of the ones we see in the workshop.

Drop us an email or call us on 01782 411021 if you want a chat about what we can do for your fleet.

email us