Copper Loss and Torque Ripple Minimization in Switched Reluctance Motors Considering Nonlinear and Magnetic Saturation Effects

Abstract

The discrete torque generation mechanism and inherently nonlinear magnetic characterization of switched reluctance motors lead to unacceptable torque ripples and limit the application of these motors. In this study, a phase current profiling technique and torque sharing function are proposed in consideration of magnetic saturation effects and by minimizing power loss in the commutation area between the adjacent phases. Constant torque trajectories are considered in incoming and outgoing phase current planes based on nonlinear T-i-theta curves obtained from experimental measurements. Optimum points on constant torque trajectories are selected by improving drive efficiency and minimizing copper loss in each rotor position. A novel analytic invertible function is introduced to express phase torque based on rotor position and its corresponding phase current. The optimization problem is solved by the proposed torque function, and optimum torque sharing functions are derived. A modification method is also introduced to enhance the torque ripple-free region based on simple logic rules. Compared with conventional torque sharing functions, the resultant reference current from the proposed method has less peak and effective values and exhibits lower copper loss. Experimental and simulation results from a four-phase 4 KW 8/6 SRM validate the effectiveness of the proposed method.

Improvement of the Torque-Speed Performance and Drive Efficiency in an SRM Using an Optimal Torque Sharing Function

“…T ref ×f rise (θ) in Equation 5, which is defined by the right part of Equation (16) and the other section of TSF can then be easily obtained from Equation (6). Figure 5 shows the typical profiles of four common conventional TSFs [25]. The turn-on angle, turn-off angle, and overlap angle, θ on , θ off , and θ ov are set to 5 • , 40 • and 5 • , respectively.…”

A Review of the Methods for Improving the Efficiency of Drive Motors to Meet IE4 Efficiency Standards

“…This is illustrated by the work in [16]- [19]. Middelberg discussed the caveats to attaining high efficiency systems though implementation of the IE3 classification in [20] due to other losses in the complete mechanical and electrical system, and this will be further complicated in a variable speed system.…”

A sense winding system and dynamic current profiling to reduce torque ripple of SRM

“…1,[15][16][17] An adaptive mechanism to determine proper current profile for improved transient response and reduced torque ripple is presented in Faiz et al 18 with two phases excited simultaneously. A controller based on Lyapunov function is proposed in Sahoo et al 12 that compensates the uncertainties in the flux-linkage model and ensures fast torque error convergence.…”

“…Other TSFs that consider torque ripple minimization as primary objective and reduction of copper losses as secondary objective are proposed in previous works. 1,[15][16][17] An adaptive mechanism to determine proper current profile for improved transient response and reduced torque ripple is presented in Faiz et al 18 with two phases excited simultaneously. However, these TSF methods use rotor angle from encoder or similar position sensor to impose the TSF on the reference current.…”