基于齿部磁场分析的大型潜水电机气隙偏心故障研究

Study on Air-Gap Eccentricity Fault in Large Submersible Motors with Tooth Magnetic Field Analysis

大型潜水电机广泛用于工矿企业给排水、城市污水处理等场所,然而转轴弯曲、轴承磨损等机械故障会引起气隙偏心。气隙偏心轻则导致气隙磁场畸变、振动增大和电流波动,重则定、转子相摩擦,导致设备停机或损坏。由此推导了大型潜水异步电机动态气隙偏心状态下某一固定位置处的定子齿部磁通解析表达式,分析偏心状态下的磁通故障频率,其基本思想是认为定、转子合成磁动势和气隙磁导决定了气隙磁通的大小,而定子齿部对应位置处气隙中的磁通全部经过齿进入定子轭部,据此提出了基于齿部磁场分析的大型潜水电机气隙偏心故障在线监测方法。最后,利用有限元法对理论分析进行了验证,并对故障频率的幅值与偏心度之间的关系作了进一步探索,为异步电机动态气隙偏心的精确检测提供了依据。

Large submersible motors are widely used for water supply and drainage of industry, municipal wastewater treatment, etc. However, mechanical failures such as bent shaft and bearing damages will result in air-gap eccentricity. Small air-gap eccentricity gives rise to air-gap field distortion, increase in vibration and current fluctuation. Critical air-gap eccentricity may lead to a rub between the rotor and stator, or breakdown of the driven equipment. This paper deduces the magnetic flux expression of a stator tooth in a dynamic eccentric submersible motor, and analyzes eccentricity related frequencies in tooth magnetic field. The basic idea is that the air-gap magnetic flux is determined by the air-gap permeance and magnetomotive force, while the air gap magnetic flux near the tooth totally passes through the stator tooth. Accordingly, a way of air-gap eccentricity detection in large submersible motors is proposed in this paper. Finally, the theoretical analysis is validated by finite element simulation. This paper also explores the relation between magnitude of harmonic and degree of eccentricity, providing the precise air-gap eccentricity detection of induction motors.