The Fault Diagnosis Of A Gearbox System Based On Wavelet Analysis And The Current Signature Of The Induction Motor

The gearbox has been widely used as an necessary general components for connection and power transmitting in metal cutting machine, aviation, electric power system, agricultural machine, transport machine, metallurgical and so on. Mechanical. Because equipments become more and more maximization, high efficiency and strength, the failure of gear transmission is very complex and its forms are quite different, the failure diagnosis of gearbox transmission system has practical significance and important value. In the failure diagnosis of gearbox, vibration measurement is the basic means to collect error signals. But in practical applications, it is very hard to achieve good vibration signals because of the fixing difficulties of sensors. Recently, as the improvements of motor speed sensor-less, the motor current is used to make failure diagnosis. The current signal of induction motor can reflect the dynamic characteristics of external loads, through different current value, motor dynamic characteristics of external loads can be predicted.The paper introduces the mechanism of failure diagnosis and some examples based on the method of measuring the current of induction motor. And two signal analysis methods are emphatically present. One is the analysis of effective value, through theoretical derivation and experiments, it is proved that there are relationship between motor frequency, amplitude and loads. The experimental data are studied using wave analysis to show clearly effects. The second analysis of current component based on synchronous reference frame, through arbitrary coordinate system, establish combination loading small signal model of gear transmission system and show the expression of system transfer function. The dynamic characteristics reflecting by motor current signal is shown theoretically, and through wave analysis explain the relationship between load torque and motor current. Thus it is proved that the motor current signal could be used to make failure diagnosis of gearbox.