Effects of laminations on the vibrational behaviour of electrical machine stators

An electrical machine stator is a laminated thick cylinder. For simplicity, a homogeneous thick cylinder has often been used as a model of a stator for the purposes of vibrational analysis. Experiments show that the vibrational behaviour of a stator is quite different from that of an homogeneous thick cylinder. Among all of the vibrational modes, predicted by using the homogeneous cylinder model, only a few of them are the modes of a realistic stator, and most of the predicted modes are ones which cannot be traced experimentally. In this paper, based on the analytical results for the vibrations of solid annular plates, and the experimental results for the vibrations of laminated annular plates under a range of clamping pressures, it is found that the vibrational behaviour of a laminated thick cylinder is dominated by that of an individual cylinder lamination. Laminations have significant effects on the vibrations of a cylinder and the effects are mode type dependent. As either the number of laminations or the clamping pressure increases, all of the transverse vibrational modes of a laminated cylinder are eliminated, leaving only the in-plane vibrational modes-that is, the pure radial modes-as the only ones which persist. A laminated stator exhibits mainly pure radial vibrational characteristics, which are quite different from those of an homogeneous thick cylinder. (C) 1997 Academic Press Limited.