Brushless DC Motor with Large Airgap

Abstract

The authors propose the new brushless DC motor for pump with large airgap, 8mm, as compared with conventional gap 1mm. The conventional pump system is composed an induction motor, a magnetic coupling and a magnet rotor with the vane. This rotor is transmitted a revolution power by the magnetic coupling. In new motor, the rotor of the motor has the vane without magnetic coupling. The airgap is very large in order to equip the seal between the stator and rotor. The seal protects stator coil against liquid, such as water and chemical material. The performance of the motor were analyzed by FEM and compare with experimental results. The analyzed results agreed with experimental results with good accuracy. In the experiments using a 4-pole 0.75kW test motor and high-efficiency drive inverter with power factor control, the motor efficiency was about 88%, and the motor power factor was about 98%.