Investigations on an SYNRM coupled to a constant power load connected to a weak grid

Constant power loads like electric traction load, lathe machines, grinding machines and coiler drivers are important assets to the industry. Considering that these constant power loads are coupled to motors which are connected to weak grids where voltage dips are frequent, this paper introduces a novel analysis of the effect on speed and torque of a synchronous reluctance motor connected to a constant power load on the occurrence of a voltage dip greater than the tolerable voltage dip margin for a particular operating point. The focus of this paper is to estimate the amount of reduction in speed as well as torque and changes in the other operating quantities from the set reference values if the dc bus voltage reduces below a pre specified permissible limit. Also the method of restoration of initial operating speed on the occurrence of a voltage dip is also discussed in this paper. The proposed analysis predicting the degree of changes in all the operating quantities is validated by simulations carried out in Simulink/MATLAB environment.