Compressor

A compressor comprises a frame 2, a rotor assembly, and a heat sink assembly 5. The rotor assembly comprises a bearing assembly to which the heat sink assembly is secured. In use, air is drawn through the interior of the compressor frame. The heat sink assembly comprises a generally disc-shaped heat sink (51, figure 7), located beneath an impeller, and which extends radially from the bearing assembly into the air path through the frame such that the air flows radially, preferably inwards, over the heat sink. The heat sink may project into an underside of the impeller. The heat sink assembly may comprise a further heat sink (52, figure 7) having a plurality of legs extending radially from the bearing assembly. The legs may be evenly spaced, and may each taper in width in a direction away from the bearing assembly. One heat sink of each type may be spaced from one another along a sleeve (50, figure 7) of the heat sink assembly.