This paper describes a new experimental method for measuring stator heat transfer in a rotor–stator disc system using an electrical heater array. The system is partially blocked at the periphery, with radial outflow of rotor-pumped air from an inlet at stator centre. The aim is to improve thermal performance prediction for air-cooled disc type electrical machines. Local Nusselt numbers were measured for 0.6<r/R<1 at three non-dimensional gap ratios G=g/R=(0.0106,0.0212,0.0297) and rotational Reynolds numbers 3.7e4less-than-or-equals, slantReθless-than-or-equals, slant5.6e5. Transition at the stator is observed to occur at Reθ>3e5 for all gap ratios. Increased Nusselt numbers at the periphery are observed for all Reθ and G because of the ingress of ambient air along the stator due to the rotor pumping effect.