Research On Permanent Magnet Synchronous Motor With High Overload Performance

In some motor applications, for example, the area of aerospace, military, auto power and lathe processing, because of its size, quality, space environment adaptability, the special requirements of reliability, etc., the motor is proposed by conventional analysis and design to the requirements of the development of high output performance. The motor is expected to have high torque overload ability under the condition of invariable speed.In this paper the permanent magnet synchronous motor overload ability refers to the torque overload ability under constant speed. The Overload multiple is ratio between maximum output torque and rated output torque. Under constant speed, when the output torque of ordinary permanent magnet synchronous motor exceed rated torque, the torque output will not increase linearly following the input current, eventually develop saturated phenomenon. Because under the overload condition, the PMSM appears the phenomenon below, motor stator core saturated, strong armature reaction, strong straight axis demagnetizing, the motor temperature rising too high. In these restrict condition, it is hard to continue improving motor output capacity.In this article we consider the output power of permanent magnet synchronous motor (PMSM), and analyze the relationship between the extreme output power and extreme input current of permanent magnet synchronous motor. Emphatically we resolve the problem how to improve the extreme input current, so as to improve overload ability of the motor. In view of the above three factors, we further analyze the overload ability of permanent magnet synchronous motor influenced by the stator core saturation, the armature reaction and motor reliability.We consider the permanent magnet synchronous motor from the aspects of motor principles and motor structure. By changing the stator and rotor structure parameters, we analyze the influence to the ability of overload by the change between integer slot and score slot, the influence by the ratio of stator and rotor outer diameter, the influence by the slot/pole combination, the influence by cogging area ratio. We analyze the influence to the output capacity of permanent magnet motor by the change of magnet size and pole numbers.Then in this paper we analyze the overload ability of slotless permanent magnet synchronous motor (SL-PMSM), and we compared the overload ability between the SL- PMSM and the slot motor. The SL-PMSM has a less power density than the slot motor in the range of some stator outside diameter and volume. When the stator diameter is less than 44.5 mm, the SL-PMSM has a higher power density and stronger overload ability.Finally, according to the above analysis we design a PMSM with high overload ability, and the torque overload multiple is 10 times. Through the reasonable experiment method, we measure the torque overload multiples of this high overload motor. We draw the curve between the torque and the current, analyze the linearity of the T-I curve. We measure the motor's temperature rising curve under high overload using the temperature sensor. We compare the results between the experiment and FEM, analyze the reason, and output the conclusion.