Cooling of electrical machines
An electrical machine comprising a rotor 20 , a stator 30 and an air gap 40 arranged between the rotor 20 and the stator 30 is provided. The stator 30 or rotor 20 comprises a plurality of electrical coils 90 , wherein one or more of the electrical coils 90 carry a heat sink, wherein the heat sink is attached to the electrical coil with a thermally conductive material. Methods for modifying a temperature distribution of a stator in an electrical machine are also provided.
1. An electrical machine, comprising:
a rotor and a stator;
an air gap defined between the rotor and the stator; and
one of the stator or the rotor comprising a plurality of electrical coils,
wherein at least one electrical coil of the plurality of coils comprises a heat sink to dissipate heat to the air gap,
wherein the heat sink is attached to the at least one electrical coil with a thermally conductive material,
wherein a temperature distribution of the at least one electrical coil is more homogeneous with the heat sink attached than without the heat sink attached and a difference between a highest temperature and a lowest temperature of the at least one electrical coil is less than 20° C. with the heat sink attached.
2. The electrical machine according to claim 1 , wherein the heat sink comprises a plurality of fins.
3. The electrical machine according to claim 1 , wherein the heat sink is made of a substantially non-magnetic material.
4. The electrical machine according to claim 1 , wherein the heat sink is attached to an outside of the at least one electrical coil.
5. The electrical machine according to claim 1 , wherein the heat sink is attached to an inside of the at least one electrical coil.
6. The electrical machine according to claim 1 , wherein the at least one electrical coil is arranged around teeth, the at least one electrical coil comprising a substantially obround shape having a first straight side and a second straight side parallel to the first straight side, and a first curved portion connecting the first straight side with the second straight side at a first end, and a second curved portion connecting the first straight side with the second straight side at a second end.
7. The electrical machine according to claim 6 , wherein the heat sink is attached at the first curved portion.
8. The electrical machine according to claim 6 , wherein the second end is closer to a cooling air supply than the first end.
9. The electrical machine according to claim 6 , wherein the at least one electrical coil comprises a plurality of the heat sinks.
10. The electrical machine according to claim 9 , wherein for the plurality of electrical coils comprises a plurality of the heat sinks, a first one of the heat sinks is attached at an inner side of the first curved portion, and a second heat sink is attached at an outer side of the first curved portion, and wherein a third one of the heat sinks is attached at the second curved portion.
11. The electrical machine according to claim 1 , wherein the stator comprises the plurality of electrical coils.
12. A wind turbine comprising the electrical machine according to claim 1 .
13. A method for modifying a temperature distribution of an electrical coil in an electrical machine, the method comprising:
operating the electrical machine;
measuring a temperature distribution of the electrical coil while operating the electrical machine; and
attaching a heat sink to a selected area of a surface the electrical coil to increase a contact surface with an air flow around the electrical coil,
wherein the temperature distribution of the electrical coil is more homogeneous after attaching the heat sink than before attaching the heat sink and a difference between a highest temperature and a lowest temperature of the electrical coil is less than 20° C. after attaching the heat sink.
14. The method according to claim 13 , wherein operating the electrical machine comprises providing a cooling air flow through an air gap arranged between a rotor and the stator.