Torsional Vibration Analysis of Shaft in an Induced Draft Fan Due to Variable Frequency Drive

Abstract

The torsional vibration problem of shaft in an induced draft fan (IDF) caused by frequency conversion driving technology is a result of dynamic electro-mechanical coupling behavior during the energy conversion. Therefore, it is difficult to understand the mechanism of torsional vibration by only analyzing the mechanical structure or the electrical structure. In this paper, eigenvalue structural analysis (ESA) and time-domain transient analysis, which are typically used to examine sub-synchronous resonance (SSR), are employed to resolve this issue. It is difficult to develop a linear model for complex controllers with ESA as ESA can cause certain errors during the linearization and estimation of initial values of equilibrium points. On the contrary, time-domain analysis not only offers a small-step integration technique to simulate a realistic condition but also facilitates transient analysis of complex controllers. Transient analysis has been used to study the influence of elastic parameters of shaft, self-damping coefficients, resistance of the stator side, smooth reactance of the stator side, and voltage-frequency ratio on the control of target frequency converters and cascade multilevel high-voltage frequency converters. In this paper,It is also advised to avoid torsional resonance region with torsional-vibration monitoring during the operation of the system, and stator resistance can be added and the voltage-frequency rate can be adjusted to obtain an integrated control of an active torsional-vibration system.

Analysis, Modeling, and Simulation Solution of Induced-Draft Fan Rotor with Excessive Vibration: A Case Study

“…Modifying the rotation speed of the fan rotor in order to move it away from its natural frequency values, with the purpose of preventing resonance, was not possible due to two main factors: a) the airflow and the efficiency of the system are altered and no longer meet the functionality requirements; and b), according to Qingjie et al (2020), it is not possibleto eliminate the torsional vibration generated in this type of systems when adding a variable frequency drive. Inertial factors generate this torsional vibration due to speed changes in induced draft fans, and the torsional vibration is in turn caused by frequency conversion driving technology due to dynamic electromechanical coupling.…”

“…Inertial factors generate this torsional vibration due to speed changes in induced draft fans, and the torsional vibration is in turn caused by frequency conversion driving technology due to dynamic electromechanical coupling. Several alternatives to eliminate the torsional vibration of the shaft were considered in (Qingjie et al, 2020), finding that it is only possible to displace its resonance region and reduce its amplitude but not eliminate it.…”