Twin Synchronous Motor Grinding Mill Drives: Performance Comparison of Two Options

Abstract

The major challenge of twin synchronous motor drives, as seen in the large grinding mills of the mineral and cement industries are motor overheating and gear wearing, due to certain inevitable manufacturing errors/tolerances on the gear which prevents the two motors from sharing the mill load equally. This paper models a typical gear-driven grinding mill load which accommodates the manufacturing error located on the girth gear circumference, and applies it to two twin synchronous motor drive configurations, namely two three-phase seriesconnected six-winding synchronous motors (Drive A) and two conventional threephase synchronous motors (Drive B). The motor equations were mentioned, and the drives simulated in the MATLAB/SIMULINK environment. Results obtained for the two configurations were compared. It was observed that while the risk of motor overheating was removed in Drive A, it was obvious in Drive B. However there is a risk of motor shaft breakage due to the mechanical coupling of the motors.