Based On Negative Sequence Rotating Magnetic Field Of Induction Motor Rotor Fault Detection

Induction motors are widely used in the industrial and agricultural production as drivers. In the electrical network total load, the induction motors composes above 60% with the electric quantity.A motor failure not only can result in damage to the motor, but also can affects the normal production and life of people, which will cause financial losses and serious failure. Statistical studies have shown that the rotor broken bar fault, which account for nearly 10% of total induction motor failures, is the most familiar fault for induction motors. Consequently, researches on rotor broken bar fault diagnosis able to detect this kind of fault at an early stage and also to allow for carefully planed repair actions are of great significance.In order to guarantee the motors in good quality, enable the motors normally applied to each realm of production, most electrical manufacturing do experiment to examining if the motors are healthy, before the motors leave factory.Rotor quality examination is an important part.At present the universal method to diagnosis rotor failure use (1±2s)f_s(s isslip, f_s is electrical network frequency)frequency component as the failurecharacteristic. These methods all have obtained good effect when motors operating with load.But when motors operating without load, slip become very small, causes the failure characteristic component also very small and hard to examine.If the leaves factory examination can carried on under the condition of no-load, the experiment would be more convenient and easier to operate.This paper proposed a new method to diagnosis rotor failure when motors operating without load. The method uses three-phase imbalanced voltage source as power supply, the (3 - 2s) f_s frequency component as the failure characteristic. With thefundamental voltage component and its Hilbert transformation as elements, a reference coordinate transformation matrix is constructed. After three times reference coordinate transformation, the stator currents are transformed into triple synchronous speed rotating reference coordinate, the characteristic components are extracted, and the rotor fault is diagnosed.The same method has been used in single-phase induction machine rotor failure diagnosis.Meanwhile, the influence of unbalanced mass is analyzed and elemenated.