Electric machine with permanently excited inner stator

1. An electric machine, comprising:

an outer stator having a plurality of windings;

an inner stator having a plurality of permanent magnets and arranged within the outer stator in concentric relationship to the outer stator;

a rotor arranged between the outer stator and the inner stator in concentric relationship to the outer and inner stators and movable relative to the outer and inner stators, said rotor comprising a mounting element made from a non-magnetic material and having a plurality of recesses, with a magnetically soft segment being arranged in each of the recesses;

a first cooling device configured to cool the permanent magnets of the inner stator; and

a second cooling device configured to cool the outer stator,

wherein the first and the second cooling devices have a plurality of cooling tubes for passage of a cooling liquid, and

wherein the cooling tubes are arranged in an iron core assembly of the inner stator and the outer stator.

2. The electric machine of claim 1 , wherein the cooling tubes are uniformly distributed in a circumferential direction along an axial direction of the electric machine.

3. The electric machine of claim 1 , wherein the permanent magnets of the inner stator are made from a ferrite.

4. The electric machine of claim 1 , wherein the permanent magnets of the inner stator contain iron-neodymium-boron.

5. The electric machine of claim 1 , wherein the rotor has a pot-shaped configuration.

6. The electric machine of claim 1 , further comprising a hollow shaft, said rotor being connected to the hollow shaft.