Experimental Comparison of Acoustic Characteristics for a High-Efficiency Magnetic Gearbox and a Mechanical Planetary Gearbox for Industrial HVAC Applications

In industrial fan applications, gearboxes or belt drives are often utilized to reduce the motor footprint to an acceptable level to maximize airflow. Customers demand fans with minimal noise and maintenance requirements, as well as a large mean time to failure (MTTF); however, mechanical gearboxes and belt drives are associated with high noise levels, significant maintenance requirements, and low MTTF rates, especially in harsh environments. This article presents the development of a radial flux coaxial magnetic gear optimized for cost and modulator retention. The results reveal that sizable retaining features on the modulators' tangential sides may be employed while still maintaining high electromagnetic performance. A magnetic gear prototype was constructed and evaluated to determine its A-weighted acoustic noise characteristics. A similar commercial-off-the-shelf mechanical planetary gearbox was also evaluated to provide a benchmark for comparison with the magnetic gearbox. The results reveal the novel finding that the magnetic gearbox became quieter as the load increased, and the mechanical gearbox was louder than the magnetic gearbox at rated speed, except at very light loads. A second magnetic gearbox was also tested and proved to be louder than the mechanical gearbox; however, this second magnetic gearbox also became quieter as its load increased.