Start-up problem with an induction machine and a permanent magnet gear

This paper presents the preliminary work conducted to design a magnetic gear (MG) integrated with a fan and driven by an grid connected induction machine (IM). A start-up problem with a MG, which occurs due to a high oscillating torque and a high breakdown torque of the IM when starting up directly from grid, has been investigated. Based on a preliminary design proposal of a MG-fan system a simulation model is developed and the effect of changing different parameters has been studied. A test set-up has been build and different tests are carried out to verify the simulation model. The relation between the mass moment of inertia of the low and high speed side of the MG and their effects on the start-up problem have been examined. It is concluded by simulation that an increased mass moment of inertia on the high speed side of the MG can overcome the start-up problem, and this is verified by adding extra mass moment of inertia on the test-setup. Good agreement between the calculated natural frequency of the test system and measurements has been experienced, both with and without extra mass moment of inertia added to the system.