Practical diagnosis of induction machines operated in power plant auxiliaries

The diagnostic procedure, assisted by dedicated digital system, was elaborated to perform diagnostic investigations of induction machines. The paper presents diagnostic reports of the machines driving a coal mill, a coal- powder blaster and a water-feed pump, all installed in a power plant. Assessment of cage states was based on measurements of the magnitude of the diagnostic components in the stator currents. The measurements of these components were performed during stationary operations and during start ups. The diagnostic system consists of two subsystems. The first one secures data acquisition. It consists of current clamps, signal conditioning amplifiers, anti - aliasing filters and the notebook with ADC card. The other subsystem is a dedicated software producing diagnostic reports. The paper proves its main conclusion that it is indispensable to base the diagnosis on both the start - up and steady state currents, as the first allow to diagnose the starting and the second the working cage.