End-winding resonance, should be order or not

During the design stage of an electric motor or generator, the components are evaluated according to the operating loads.It is important that resonances are removed in relation to the excitation frequencies to avoid amplification of vibration that will increase mechanical loads that could lead to premature fail.For evaluation of the rotor, lateral and torsional analyses are performed to find the natural frequencies. Similarly, the natural frequencies of the static part are conducted for housing, cover, and stator core.However, the end-winding has innumerous nonlinearities, multiple types of fastening, different types of materials, and fibers that are dependent on the impregnation process to achieve the correct stiffness to support the coils. In this way, to have precise results, it is necessary to measure the natural frequency of the end-winding. This paper presents the evaluation of natural frequency of end-winding of 50 electrical machines.