Research of vibrations in induction machines during transient processes using a Ferraris sensor

Abstract

The electrical torque of an induction machine cannot be measured by electrical units of current and voltage, the only possibility is to measure shaft torque and angular acceleration of the rotor mass. The shaft torque is measured with strain gauges, which are electricaly coupled in a Wheatstone bridge. The angular acceleration of the rotor mass is measured with a specially designed Ferraris sensor. For both signals the delay time has to be taken into account and adjusted by an electrical network. The test rig with the mentioned sensor and their parameters are presented in the paper. The electrical torque was measured during runup and reversing of the speed of the induction machine. By variation of the diameter of the shaft and the flywheel mass different resonance frequencies of the system could be realized. The measured signals were processed by using the Fast Fourier Transformation (FFT) analysis method to show the sweep excitation of the mechanical system by the electrical torque of the induction machine.