Energy loss due to unbalance in rotor–shaft system

Abstract

Purpose One of the major problems faced by industry is vibrations in rotating parts. Vibration is a to-and-fro movement of rotating mechanical parts and has many detrimental effects on machinery. It is obvious that no movement can be achieved without consumption of energy. All the energy consumed in vibration of mechanical parts is useless. Unbalance is one of the most common reasons for vibrations. This paper aims to experimentally evaluate the effect of unbalance in a shaft–rotor system on power consumption. An experimental setup consisting of a shaft and a rotor mounted on antifriction bearing was built-up. The shaft was driven through a flexible coupling, by a variable speed DC motor. The shaft–rotor system was rotated at different speeds and electrical power consumed by the system was measured at specific speeds varying from 1,200 to 2400 rpm. The rotor was balanced to grade G6.3 at 1,200 rpm. The power consumption by shaft in balanced condition was taken as baseline data for the further work. The rotor was then made unbalanced by adding different masses at 60 mm radius, and power consumption was recorded again at the same speeds. It was observed that average power loss due to unbalance is of 0.11watt/gm.mm unbalance. This can amount to 2.75 kw if there is unbalance of 50 gm at a radius of 500 mm. This work is meant to emphasis on the fact that the power consumption can be reduced if the vibrations can be kept under control.