Coil Arrangement to Reduce AC Copper Loss by Applying Strand and Transposition of Ultra-high-speed Motor for Air Compressor of Fuel Cell Vehicle

다국어 초록 (Multilingual Abstract)

An internal combustion engine vehicle emits various harmful gases and causes environmental problems such as global warming. Therefore, research and development of eco-friendly vehicles have being actively conducted in recent years. An air compressor that intakes and compresses air from the atmosphere at an appropriate pressure and flow rate is used to drive a fuel cell vehicle among various eco-friendly vehicles. Air compressors are required to be high efficiency and power density due to size constraints. It is powered by an ultra-high-speed motor with small volume, weight and high energy density [1]. Ultra-high-speed motor is driven by high-frequency current. However, owing to the high current frequency, the AC copper loss in the stator winding is large which affects the efficiency of the motor [2].
This paper proposes a coil arrangement method for reducing copper loss occurring in the motor by applying strand and transposition. The target motor is 2-pole, 6-slot, ultra-high-speed motor and was designed considering the slot liner and the copper insulation. The AC copper losses that occur in no strand, strand and strand transposition are compared and analyzed under the same conditions of current density and fill factor. In the slot of the motor, the magnetic field distribution imbalance due to the leakage magnetic flux causes the skin effect and the proximity effect. When the winding of the motor is no strand, the AC copper loss occurs the most. When a strand was applied, AC copper loss decreased by increasing the total effective cross-sectional area of the coil compared to no strand. Additionally, AC copper loss was reduced by reducing the impedance difference between strands by applying a transposition [3]. As a result, AC copper losses are smallest at the strand potential.