Principle and basic characteristics of hybrid variable-magnetic-force motors

Reduction in power consumed by motors is required for energy saving in electrical appliances and electric vehicles. The motors used in such appliances and vehicles operate at variable speeds. For reducing energy consumption of electrical appliances, the flux-weakening current that depresses the voltage at high speed leads to significant copper and core losses. Therefore, we have developed a new technique for controlling the magnetic force of a permanent magnet on the basis of the load or speed of the motor. In this paper, we propose a novel motor that can vary the magnetic flux of permanent magnets and clarify the principle and basic characteristics of the motor. Our motor has a permanent magnet magnetized by magnetizing coils of the stator. The results show that the motor can vary magnetic flux linkage from 37% to 100% and produce high torque. In addition, when positive field current flow in the magnetizing coils as a field coil, maximum torque increases by 25 %. Also, the induced voltage can decrease to 0 V by negative field current. The results of our analysis prove that our novel motor can vary the flux of a permanent magnet on the load and can be used in a variable-speed drive with high performance.