Measuring circuits of rotor eccentricity diagnostic system
The purpose of the article is to show that the measuring circuit in the form of a measuring bridge powered by a high-frequency generator is most suitable for electric machine diagnostic system implementation. Rotating electric machines are widely used for electrical energy production in electric power industry, and as drives of various types of mechanisms. One of their most common damage is the static eccentricity of the rotor arising either due to bearings destruction or to the displacement of risers where the bearings are installed. It is a usual practice to detect the given type of damage using eccentricity diagnosing systems, in which the currents and electromotive force in the windings are used as information about the damage (despite the undoubted benefits of these devices they don’t have wide distribution). It is caused by the fact that a simple diagnostic system reliably detecting (irrespective of the fluctuations of the parameters of the supply main and load) the presence and displacement value of the rotor shaft is still not developed. These shortcomings can be overcome through the use of the diagnostic system, in which the rotor displacement is controlled by a capacitive measuring converter and the corresponding measuring circuit. The analysis of the design features of electric machines has shown that it is advisable to make a measuring converter a device, one of the electrodes of which is the surface of the shaft or the rotor core, and the other - the electrode in the groove wedge or a special insulated housing. It is found out that the implementation of the diagnostic system with the measuring converters is possible only when using a measuring circuit built on the principle of a voltage divider, a resonator cavity, a capacitive-type circuit or a measuring bridge. Further selection of the measuring circuit and its location in the machine is carried out on the basis of the measuring converter design and the interference protection method. It is determined that a measuring circuit in the form of a measuring bridge powered by a high-frequency generator where the measured signal is a filter with the same frequency is the most suitable for diagnostic system implementation. The final choice of the measuring circuit diagram for further preferred consideration and development of electric machine rotor eccentricity diagnosis is based on its usability, measurement accuracy and sensitivity.