Arrangement for deep cooling a field winding in the rotor of an electric machine

An arrangement for cooling the field winding of an electric machine to be deep cooled is provided with a rotating mixing chamber containing vaporous and liquid coolant and with a centrifugal pump between areas of different temperatures to pump gaseous coolant out of the mixing chamber. The maximum flow cross section of the colder line part of the centrifugal pump is at the most half the size of the maximum flow cross section of the warmer line parts and/or at least the end piece of the colder line part is thermally coupled to colder parts of the rotor to prevent pump instabilities caused by coolant convection.