Abstract
A combined electromagnetic and thermal modelling approach has been developed to optimise the design of multiple radial stator vents in an air-cooled, synchronous generator with a power rating of several hundred kVA. An experimentally validated 3-D Conjugate Heat Transfer Computational Fluid Dynamics model has been created and coupled with 2-D Electromagnetic Finite Element Analysis. Correlations between the combined vent width and rotor copper, rotor iron and stator iron losses were derived from the electromagnetic analysis. These correlations were implemented into the optimisation procedure of the parametric thermofluid model. Five parameters: vent locations, widths and the height of a baffle, were optimised simultaneously with the aim of minimising the peak stator winding temperature. The peak stator winding temperature was reduced by 11.1 %. The average stator winding temperature decreased by 6.3 %. To maintain the machine's power output, the removal of active stator material was compensated by increasing the rotor current.
Highlights
WITHIN this paper, a synchronous generator with a power rating of several hundred kVA has been analysed using a multi-physics approach to establish the potential performance gains that adding radial stator vent airgaps may provide
This concept has general validity and is applicable to any type of electrical machine, in this paper the analysis is focused on a salient-pole, wound-field synchronous generator with a power rating of several hundred kVA
This is well proven by the comparison between Finite Element Analysis (FEA) and experimental copper losses, shown in Fig. 1, where the percentage error at full-load operation is equal to 0.5%
Summary
WITHIN this paper, a synchronous generator with a power rating of several hundred kVA has been analysed using a multi-physics approach to establish the potential performance gains that adding radial stator vent airgaps may provide. Designing the placement, sizing and number of these vents is a highly complex and inter-disciplinary engineering problem, as a different split of air flow through the airgap, barrel gap or vent passages can cause a change in both the temperature and loss distribution. For this reason, approaches which are based on correlations cannot provide accurate predictions. Computational Fluid Dynamics (CFD) is the only modelling approach capable of predicting turbulent flow, convective and conductive heat transfer simultaneously. It has been chosen for the thermal modelling in this investigation. The electromagnetic losses are simplified down to correlations which have been implemented as input parameters for the thermal optimisation procedure
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