FIG. 2 illustrates components of a drive motor and battery thermal management system, both constructed and operating.

During operation, electric motors can generate significant amounts of heat, especially by the traction motor of a vehicle where size and weight constraints are coupled with the need for high power output. Electric motor overheating causes the motor winding insulation to deteriorate quickly. Another issue caused by overheating is that permanent magnets in the rotor lose their magnetic properties as they overheat, resulting in a loss of efficiency.

That is why it is important to cool the internal motor components as well as the outer motor components. The electric motor cooling system must operate efficiently over large variations in ambient operating environment as the electric motor may be subjected to a wide range of ambient temperatures, humidity levels, and/or dust/dirt levels.

Tesla took a number of different approaches to meet the cooling demands placed on a vehicle's electric motor in his earlier patented inventions. But, these prior solutions had a number of shortcomings. They failed to address the differing heat production locations along the length of the rotor. More heat tends to be generated in the central portion of the rotor, as compared the end or distal portions of the rotor.

Another problem with the operation of battery powered electric vehicles is that the powering batteries do not operate efficiently at low temperatures.

Therefore Tesla improved the system and filed a patent "Electric motor waste heat mode to heat battery"

Filed: March 9, 2020
Published: November 5, 2020


FIG. 3 illustrates components of a drive motor and a portion of the components of a drive motor thermal management system according to a disclosed embodiment.

In a waste heat mode, the drive motor electronics power the stator without causing rotation of the rotor. Further, in the waste heat mode, the drive motor fluid pump at least partially fills the hollow cylindrical body with the fluid to force the fluid from the hollow cylindrical body via the fluid exit ports to spray upon the stator end-windings and to extract heat from the stator end-windings. Still further, the drive motor fluid pump circulates the fluid to a heat exchanger for heating a battery.

With the electric motor of the present disclosure, a fluid is heated by the end-windings of the stator while the rotor is stationary and the captured heat is used to heat the battery. Thus, a separate battery heating structure is not needed, reducing complexity and expense of a machine serviced by the electric motor and battery.

According to a second embodiment of the present disclosure, a method for operating an electric motor includes powering a stator of the electric motor to heat end-windings of the stator without or without causing a rotor of the electric motor to rotate. In doing so, heat is induced on the stator. The method further includes pumping fluid into a hollow cylindrical body of the rotor via a fluid feed tube and out of the hollow cylindrical body of the rotor via a plurality of fluid exit ports. The fluid may be directed to the outer diameter of the end rings. Some of the fluid may also flow on or through the stator (channel cooling).

The combination of one or more of the stator cooling and rotor cooling provides benefits in collecting waste heat in a waste heat mode that may be used to heat a battery, a cabin, and / or other components of the vehicle. The method then may include pumping the heated fluid to a heat exchanger for subsequent use in heating the battery or the cabin.

The method serves to heat fluid by the stator end-windings and using the heated fluid to heat a battery. With the fluid flow of this method, a single operation supports battery heating. Thus, a separate battery heating method is not needed.

This invention solves a number of important problems when using a Tesla vehicle, including significantly increasing efficiency and reducing the complexity and cost of the machine powered by an electric motor and battery.

© 2020, Eva Fox. All rights reserved.