Improvement in Torque Density by Ferrofluid Injection into Interior Permanent Magnet Synchronous Motor

An interior permanent magnet synchronous motor generally injects adhesive like a bond into the magnet tolerance to prevent vibration between the permanent magnet and the magnet tolerance. In this case, there is a disadvantage that magnet tolerance does not contribute to performance. In this paper, a method to improve the torque density by inserting ferrofluid to utilize magnet tolerance was proposed. When inserting ferrofluid into magnet tolerance, it is important to fix the magnet because it does not use an existing adhesive, and it is important that ferrofluid does not act as a leakage path in the insertion space. In this study, a new rotor configuration using injection plastic that satisfies these considerations was introduced. The analysis was conducted through finite element analysis, and the analysis results and experimental results were compared through dynamo test to verify this study. It was confirmed that no-load back electromotive force increased in the final model through ferrofluid injection.