{'fraction_non_alphanumeric': 0.011799410029498525, 'fraction_numerical': 0.003687315634218289, 'mean_word_length': 5.004424778761062, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Acoustic Noise Analysis of a Magnetically Geared Permanent Magnet Generator

Recently, permanent magnet machines integrated in magnetic gears have been subject to research as it is possible to construct electrical machines with impressive torque densities. A 3.5 kW demonstrator of a magnetically geared permanent magnet generator is constructed and tested for potential implementation in a small wind turbine. However, acoustic noise at an unpleasant level is present during operation of the demonstrator. This paper investigates the origin of this acoustic noise as very limited knowledge in the area is present in the literature. A reduction in sound pressure level of 13 dB(A) is obtained by enclosing the initially open end shields of the machine with 3D-printed plugs. Analysis of electromagnetic forces in the air gaps has shown that the forces acting on the steel segment rotor are the noise source whereas improvements in the mechanical design is tested and a reduction of the acoustic noise is measured. Furthermore, a new retainer for the segment rotor is designed in glass fibre to decrease cost and number of parts to be manufactured. Also, the noise from the machine with the new retainer installed is compared to the noise from the original machine to determine if the new construction and material changes the dampening of the segment ring.