A novel and precise on-line digital measurement of unsaturated phase inductance of a switched reluctance motor

Abstract

This paper presents a simple and accurate method for the on-line measurement of the unsaturated phase inductance of a switched reluctance motor (SRM). The basic principle behind the approach is to obtain the instantaneous flux linkage of the phase, which when divided by the instantaneous current of the corresponding phase will dynamically generate the phase inductance for that rotor position. A numerical division process, based on Newton-Raphson (N-R) iterative method, has been implemented using the sensed current and estimated flux linkage on an FPGA platform to generate the inductance value at each instant. It is ensured in the practical implementation that the iron parts do not saturate. It has been also verified through simulation using standard finite-element method (FEM) software packages. Further, it has been established that the effect of mutual inductance is negligibly small. The proposed method will give the true value of the unsaturated inductance of the phase identified for diagnosis/measurement. Practical results, for the experiments conducted on an existing 4 kW, 1500 rpm Oulton-make SRM, have been also presented. They are further validated against the results obtained from FEM analysis and against previously published results of the phase inductance values for this SRM. The results are found to be in very good agreement.

Dynamic Modelling and Current Control for Switched Reluctance Motor Drives in Electric Vehicles

“…The SRM utilized in this study is a classical 4-phase 8/6 machine. The non-linear properties of the machine are derived through a sequence of static two-dimensional finite element analyses based on the FEMM4.2 program [17,18]. After solving for machine parameters, the values are readily available in the results part of FEMM4.2 software.…”

Reduction of Torque Ripple in Switched Reluctance Motor Drives Through Optimum Commutation Angles Control

“…It considers current, self-inductance 𝐿 (𝑖, Ө), and inductance variation due to current to account for the effects of magnetic saturation. The £ symbol stands for the back-emf of the machine [12].…”

“…The SRM utilized in this study is a classical 4-phase 8/6 machine [12,13]. The non-linear properties of the machine are derived through a sequence of static two-dimensional finite element analyses based on the FEMM 4.2 program [14].…”

“…With the obtained (λ-i-θ) characteristics and (T-i-θ) characteristics and using Eqs. (1) to (12). The non-linear SRM simulation is built based on the current I (λ, θ) and the torque T (θ, i) look-up tables.…”

A simple approach for the computation of magnetic characteristics of 4-phase switched reluctance motor

“…The gate signals for IGBT switches in the converter are generated by FPGA processor. In the conventional method, phase inductance was measured by flux linkage characteristic values [28], [29]. As a reason, the accuracy of phase inductance proportional to the fidelity of measured voltage and current readings.…”