Optimized cooling system for a brushed electrical machine, and a corresponding method

1. A cooling system for a brushed electrical machine comprising a rotor and a commutator, the cooling system comprising:

a cooler configured to cool down the rotor and the commutator,

a first temperature monitoring device adapted to monitor a commutator temperature,

a second temperature monitoring device adapted to monitor a rotor temperature, and

a controller being configured to adjust a cooling effect of the cooler in response to the monitored rotor and commutator temperatures,

wherein the controller comprises a control algorithm where at least one output value of the control algorithm depends both on the commutator temperature and on the rotor temperature.

2. The cooling system according to claim 1 , wherein the cooler comprises a fan and an auxiliary motor configured to rotate the fan, and the controller is configured to adjust the rotational speed of the auxiliary motor.

3. The cooling system according to claim 1 , wherein the first temperature monitoring device comprises an inductive sensor.

4. The cooling system according to claim 1 , wherein the first temperature monitoring device comprises an IR sensor.

5. The cooling system according to claim 1 , wherein the first temperature monitoring device comprises a temperature sensor connected to a brush bridge.

6. The cooling system according to claim 1 , wherein the first temperature monitoring device comprises a thermal motor model.

7. The cooling system according to claim 1 , wherein the second temperature monitoring device comprises a thermal motor model.

8. A method for optimizing a brushed electrical machine having a cooling system, the brushed electrical machine comprising a rotor and a commutator, and the cooling system comprising a cooler configured to cool down the rotor and the commutator, the method comprising the steps of:

monitoring the commutator temperature,

monitoring the rotor temperature, and

adjusting the cooling effect of the cooler in response to the monitored rotor and commutator temperatures, wherein at least at one instant the adjustment depends both on the commutator temperature and on the rotor temperature.

9. The method according to claim 8 wherein the cooler comprises a fan, and the method further comprises the step of adjusting the rotational speed of the fan.

10. The method according to claim 9 , wherein the fan is rotated at a relatively high speed when the rotor temperature is above a first threshold value.

11. The method according to claim 10 , wherein the fan is rotated at a relatively low speed when the rotor temperature is below the first threshold value, and the commutator temperature is below a second threshold value.

12. The method according to claim 11 , wherein the fan is rotated at a relatively high speed when the rotor temperature is below the first threshold value, and the commutator temperature is above a third threshold value.

13. The method according to claim 12 , wherein the fan is rotated at a speed between the relatively low and the relatively high speeds when the rotor temperature is below the first threshold value, and the commutator temperature is between the second and the third threshold values, the rotational speed of the fan being adjusted to maintain a certain reference temperature inside the electrical machine.

14. The method of claim 8 , wherein at least at one instant the adjustment depends both on the commutator temperature and on the rotor temperature.

15. The cooling system according to claim 1 , wherein the first temperature monitoring device monitors the commutator temperature from a non-rotating object.

16. The cooling system according to claim 1 , wherein the second temperature monitoring device monitors the rotor temperature from a non-rotating object.

17. The method according to claim 8 , wherein the commutator temperature is monitored from a non-rotating object.

18. The method according to claim 8 , wherein the rotor temperature is monitored from a non-rotating object.