This technology features an electric motor structure that reduces shaft voltage by inserting a conductive shield around the shaft between the stator end windings and the rotor, and connecting this shield to the stator end and the grounded frame to adjust parasitic capacitance between the windings and the rotor.
A significant portion of motor failures are caused by bearing damage, with electrical discharge machining (EDM) due to shaft voltage identified as a primary cause. Ceramic bearings are expensive and have lower mechanical durability, while installing insulation or using common-mode voltage reduction methods requires additional filters for motors or inverters, leading to disadvantages in cost and structural complexity.
This technology places cylindrical copper shields on both sides of the rotor without obstructing the air gap between the stator and rotor, significantly reducing the end winding-to-rotor capacitance that causes shaft voltage while maintaining motor performance. It prevents bearing EDM through simple shield insertion without the need for additional filters or expensive bearings. Applicable to inverter-driven industrial motors and electric vehicle drive motors, it extends bearing replacement cycles and reduces maintenance costs.
This invention was developed with support from the Ministry of Trade, Industry and Energy for the development of core technologies for 5kW-class high-power-density motors for electric vehicles using a hybrid approach of non-rare-earth and rare-earth magnets.
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