Investigation of ferrofluid cooling in modular permanent magnet machines

This paper investigates an advanced cooling approach using ferrofluid as coolant to fill in the cavity around end-windings and flux gaps. The multiphysics modelling in this paper has shown that the influence of the flux gaps on machine thermal performances comes from two aspects: (1) the gravitational effect, the flux gaps allow more self-circulated coolant to transfer the heat to the housing. This helps to reduce machine temperature by around 5℃ for a flux gap width of 2mm. (2) the magnetic body force, i.e., the thermomagnetic effect. This is very effective in non-modular machine cooling. But its efficiency slightly deteriorates in the modular machines. This is because the self-circulation of ferrofluid in the flux gaps due to the gravitational effect has been negatively affected by the thermomagnetic effect.