Dynamic Behaviour and Magneto-Mechanical Efficiency of a Contactless Magnetic Transmission

This paper addresses the analysis of torsional dynamic behaviour in a magnetic transmission, where the torque is transferred in a contactless way between two coaxial rotors with permanent magnets through the interaction with a modulator element holding ferromagnetic poles. This transmission device is called planetary magnetic gear (PMG), due to its topological and functional similarity with a planetary mechanical gearing device, from which the same working principles are derived. A test bench for testing the magneto-mechanical efficiency of the PMG prototype has been designed and realised. The PMG planetary arrangement allows the possibility to test different configurations, as regards the input/output power, and the prototype dynamic behaviour has been tested as a torque multiplier or as a speed multiplier. No-load tests have been performed, evaluating the torque losses due to bearing dissipations inside the transmission, proving that the efficiency is practically independent from the power direction, in contrast with the traditional mechanical transmissions. The results here presented can be considered as an overview of a wider activity since, a design of experiment (DOE) with different loads, different speeds at the two sides of transmission and different transmission gear ratios will be further investigated, to assess the independency of efficiency from external conditions.