Abstract
This paper reports an experimental investigation into the ventilation characteristics of the air gap/radial duct combination in electrical machines. The problem is basically of the manifold type in which the machine air gap is compared to the supply duct and the radial ventilating ducts represent the branches.
The factors affecting the pressure drop and flow distribution arising from the change in air direction from circumferential in the air gap to radial in the ventilating ducts are examined. First, the influence of slot wedge and duct spacer position, relative to the air gap, was observed in a qualitative manner using a water table model; the resulting flow patterns are illustrated. Second, the same duct configurations were tested in a model of a stator segment using air as the working fluid. The results of pressure drop and mass flow distribution are presented for variations in gap static and dynamic pressures together with curves showing the distribution of pressure losses along the ducts. Finally comparisons are made between model and full-scale measurements with a brief assessment of instrument problems.
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