Enhancement of thermal contact conductance between metal surfaces in an induction motor

The thermal contact conductance between an Al-alloy pipe and the stator of an actual motor squeezed into the pipe was experimentally measured. The sta tor had a diameter larger than the nominal diameter of the housing. When th e stator diameter was 0.18 mm larger than the nominal diameter of the pipe, the thermal conductance was about 3.1 times that of an Al-alloy pipe under no pressure at the contact surface of the pipe and stator. Plates test specimens were used to confirm the effect of thermal compound s uch as silicone on the thermal contact conductance. It was found that the t hermal conductance increases when the thermal compound fills up the space b etween the two metal plates. The contact conductance between the metal surf aces with thermal compound was 3.7 to 9.4 times higher than that of a metal surface without thermal compound. Moreover, it was found that the contact conductance decreases when a PET (polyethylene terephthalate) film is used on the metal surfaces. The contact conductance of the test plates slightly decreased with an increase in the PET film thickness from 0.19 to 0.35 mm.