A new oval shaft, high performance, 2 pole line start synchronous reluctance machine for submersible pump applications

Abstract

In this paper, a 2 pole, 4 kW, 6 inches diameter line start synchronous reluctance machine (LS-SynRM) as a submersible water pump motor is designed and optimized with a new oval shaft structure. The aim is to improve the machine performance by widening the flux path on the rotor via narrowing down the shaft on the q-axis. This way a wider d-axis flux path is obtained, and accordingly, the d-axis inductance, the saliency ratio Ld∕Lq, and the inductance difference Ld–Lq are increased. First, a set of structural analyses is carried out on a 7-flux barrier rotor in 3 stages: modal, harmonic, and static structural analyses. According to analysis results, the safe limit for the shaft size reduction is determined as 8 mm to avoid excessive deformations and undesired vibrations due to resonance. Later, the machine is optimized using Multi-Objective Differential Evolution (MODE) algorithm with a narrower shaft. The quality of the Pareto front solutions shows that the oval shaft machine is superior to the circular shaft machine in terms of efficiency, motor mass, and torque ripple. The maximum recorded efficiency improvement for the same size LS-SynRM is 4 points and the same size commercial induction machine is around 20 points.

Modified Induction Machine Equivalent Circuit Including Solid Shaft Eddy Currents

“…P C = P nl − (P f w + P cu ) (10) where P nl is the measured no-load power, P cu is the stator copper losses, P fw is the friction and windage losses, and finally, P C represents the core losses.…”

“…Here, G C is the core loss conductance in Siemens, and it is represented in Equation ( 20). P C is the total core loss in watts, as determined in Equation (10).…”

“…The saturation level merely depends on the loading condition and the rotor geometry. This effect is more significant in two-pole induction machines with longer axial lengths and large shaft diameters [10,11].…”

Investigating the Role of Stator Slot Indents in Minimizing Flooded Motor Fluid Damping Loss

“…In [15], the relative viscosity variation of the water with respect to the pressure and temperature is investigated, and at room temperature, the viscosity variation of the water is reported as less than 1% when pressure changes from 0 to 300 atm. In [16,17], line start synchronous reluctance machines are designed as flooded water pump motors where the damping effect is reflected in the total loss calculation to obtain accurate performance metrics. However, results are not conducted with any experimental verification for either of the mentioned studies.…”