Torsional issues related to variable frequency control of elastic drive systems

Abstract

Systems with variable frequency drives may experience torsional vibration. One reason is the pulsating nature of motor torque due to converter supply, another one is the electro-mechanical interaction and the effects of closed loop control. This paper deals with the speed control of elastic drive systems, mainly from torsional performance point of view. Modeling of elastic shaft string is being explored. The importance of control engineering to minimize the torsional vibration is explained. The paper also discusses different control strategies and their practical use in large resonant drive systems. Key factors in this part are complexity of the controller, its robustness and availability of required parameters. The practical aspects of the implementation in real control hardware are being considered. Attention is also paid to detection and monitoring of vibrations. Finally a verification method for correct parameterization on site is proposed. Different aspects are illustrated on simulations and calculations as well as on a real 6.1 MW compressor drive

Torsional Vibration Mitigation by Harmonic Inversion through SPWM Carrier Signal Control

“…There are various methods and equipments to measure or detect torsional vibrations, like accelerometers [5] antonino.digerlando@polimi.it, khaled.elshawarby@polimi.it, gianmaria.foglia@polimi.it, roberto.perini@polimi.it acceleration sensors [6]. Oscillations can be also observed or detected, without direct mechanical measurement, from the motor speed, torque, flux or current [7], or from the error in the dc voltage or the generated power [2] [8].…”

High Speed Electrical Drives – Perspective of VFD Manufacturer

“…Therefore, torque ripple of the VFD driven motor shall be kept within certain limits. More important than the overall peak-peak torque is however the frequency spectrum of the motor torque [12,13]. The frequency content of the motor torque defines if torsional modes of the shaft string will be excited or not.…”

Dynamical processes in a multi-motor gear drive of heavy slabbing mill

“…Equivalent load sharing in MMDS can be improved by electric drive control [38][39][40][41][42] and active damping of torsional vibrations [43][44][45][46][47][48][49]. However, these methods are applicable for only two masses gearless drive systems (motor and rolls) and are not quite suitable for parallel electrical drives control in slabbing mill.…”