Arrangement for cooling of an electrical machine

1. An arrangement for the cooling of an electrical machine, comprising:

a first cooling-system connected to the electrical machine, the first cooling-system directly cools the electrical machine;

a second cooling-system connected to the first cooling system; and

a third cooling-system connected to the first cooling system,

wherein the first cooling-system circulates a first cooling-medium,

wherein the first cooling-system delivers heat to the second cooling-system, while the second cooling-system circulates a second cooling-medium to remove the received heat, and

wherein a third cooling-system which is a refrigeration-system additionally cools down the first cooling-medium,

wherein the third cooling-system is a vapor-compression refrigeration-system,

wherein the third cooling-system comprises an evaporator, and

wherein the evaporator is used to connect the first cooling-system with the third cooling-system,

wherein the third cooling-system comprises the evaporator, a compressor, a condenser which is air-cooled or water-cooled, and an expansion valve, and

wherein heat is transferred to a used cooling-liquid by the evaporator and then transferred to the third flow of ambient air via the condenser.

2. The arrangement as claimed in claim 1 , wherein the third cooling-system is selected from the group consisting of an absorption-cooling-system, a magnetic-cooling-system, and a Peltier-cooling-system.

3. The arrangement as claimed in claim 1 , wherein the first cooling system comprises a first fan to enforce a first flow of cooling-air through a generator.

4. The arrangement as claimed in claim 1 , wherein the first cooling system further comprises a pump to enforce a second flow of a cooling-liquid through the generator.

5. The arrangement as claimed in claim 1 , wherein the second cooling-system comprises a second fan to enforce a third flow of ambient air through the second cooling-system.

6. The arrangement as claimed in claim 1 ,

wherein the first cooling-system further comprises a bypass, and

wherein the bypass is used so that the first flow or the second flow can bypass the third-cooling-system.

7. The arrangement as claimed in claim 1 , wherein the electrical machine is a generator.

8. The arrangement as claimed in claim 7 , wherein the generator is located inside a nacelle of a wind-turbine.

9. The arrangement as claimed in claim 1 , wherein the electrical machine is located offshore.

10. The arrangement as claimed in claim 1 , wherein the electrical machine is located at a hot site.

11. The arrangement as claimed in claim 1 , wherein the electrical machine is located offshore and/or at a hot site.

12. The arrangement as claimed in claim 1 , wherein an existing system with the first cooling-system and the second cooling-system is retro-fit with the third cooling-system.

13. The arrangement as claimed in claim 1 , wherein the third cooling-system is a two-step refrigeration system.

14. The arrangement as claimed in claim 1 , wherein the third cooling-system is an absorption cooling-system.

15. The arrangement as claimed in claim 1 , wherein the first cooling-system is connected with the second cooling-system via a heat-exchanger.

16. The arrangement as claimed in claim 15 , wherein the heat-exchanger is an air-to-air heat-exchanger.

17. The arrangement as claimed in claim 15 , wherein the heat-exchanger is a liquid-to-air heat-exchanger.