Analysis of the Operation of a Synchronous-Reluctance-Motor-Driven Centrifugal Pump Under Frequent Voltage Dips

This article analyzes the effect of voltage dip on the output of a centrifugal pump driven by synchronous reluctance motor drive. The focus of this article is to estimate the reduction in speed if a voltage dip occurs, which exceeds the voltage dip margin, beyond which the motor would not be able to meet the load demand. It is observed that up to a certain voltage dip magnitude, speed and torque are not affected; however, beyond this magnitude, both speed and torque get reduced. The current locus diagram of the synchronous reluctance motor driving pump load is utilized to evaluate the changes in torque and speed of the motor after the occurrence of a voltage dip. A new control strategy is also proposed to restore the original speed even when less voltage is available at the motor terminals. Mathematical equations concerning the voltage dip margin at every operating point are derived. The proposed analysis pertaining to the degree of changes in all operating quantities is validated by simulations and experiments so that drive users are aware of the possible reduction in the fluid discharge owing to the presence of sustained voltage dip at the motor terminals, which is common in any weak grid.