Analysis and control of rotor eccentricity in a train-lighting alternator

Shaft breakage in three phase inductor-type brushless alternators used in Indian trains for coach lighting and air conditioning is a serious issue in a country where, about 3 million people depend on Indian railways daily as their means of transport. Shaft breakage can be due to mechanical reasons and in many cases due to rotor eccentricity and associated Unbalanced Magnetic Pull (UMP) developed in rotor. This paper presents the analysis of the alternator operation under different eccentric conditions using Finite Element (FE) method. A feedforward controller scheme is also proposed to mitigate UMP due to static eccentricity.