New Digital Multispeed Method for Indirect Measurement of Transient Electrical and Shaft Torques

This paper presents characteristics and solutions to some practical problems concerning the new digital Generalized Indirect Multispeed Method (GIMSM), for measurement of transient electrical and shaft torques occurring in a complex serial multimachine AC drive system. The method indirectly includes torsion and internal machine and shaft damping. It is based on the measurement of the transient speeds, using high resolution digital tachometers, of every lumped inertia component. Obtaining the torque values requires digital filtering, followed by numerical differentiation and integration. This procedure depends on the type of the transients and the electrical and mechanical characteristics of the drive. The measurement of transient torques using the proposed method is realized in the laboratory on a two-machine induction motor (IM) drive. The results of the measurements of the electrical and shaft torques during the acceleration and speed reversal are presented in this article. The article further recommends the choice of optimum sampling rate and the algorithm for digital filter selection based on time–frequency analysis.