Dispositivo baseado em acelerômetros capacitivos para monitoração de máquinas rotativas.

Abstract

This work addresses a device for monitoring rotating machines. The device is based on capacitive accelerometers mounted in a disc that rotates with the shaft of the machine. The device presents low-cost multi-function and can be utilized as a tool for control and predictive maintenance in rotating machines drive systems. The mathematical model of the device is developed and evaluated by simulations and experimentally. An algorithm for compensation of the errors of mounting is also developed. The device is used for measurement of position, velocity and acceleration. To extract these variables from the accelerometers’ signals is necessary to utilize techniques of phase detection and frequency of the signals, which are related with position and velocity of rotating shaft. Besides, models for extraction of the rotating axis vibration signal are proposed and analyzed. The device is used to determining the resulting torque in a 3-phase induction motor and in a variable reluctance motor. The calculation of the torque is performed based on signal from the tangential accelerations. The torque obtained is compared with the signal of the commercial torque measurement system. On the other hand, factors such as power supply unbalancing or short-circuit in turns of stator windings cause torque ripples. In agreement to this, experimental results were obtained by using the device in a 3-phase induction motor drive system at load applied with turn-to-turn short-circuit.