Fault-Tolerant Multilevel Converter to Feed a Switched Reluctance Machine

The switched reluctance machine (SRM) is one of the most interesting machines, being adopted for many applications. However, this machine requires a power electronic converter that usually is the most fragile element of the system. Thus, in order to ensure high reliability for this system, it is fundamental to design a power electronic converter with fault-tolerant capability. In this context, a new solution is proposed to give this capability to the system. This converter was designed with the purpose to ensure fault-tolerant capability to two types of switch faults, namely open- and short-circuit. Moreover, apart from this feature, the proposed topology is characterized by a multilevel operation that allows improvement of the performance of the SRM, taking into consideration a wide speed range. Although the proposed solution is presented for an 8/6 SRM, it can be used for other configurations. The operation of the proposed topology will be described for the two modes, fault-tolerant and normal operation. Another aspect that is addressed in this paper is the proposal of fault detection and diagnosis method for this fault-tolerant inverter. It was specifically developed for a multilevel SRM drive. The theoretical assumptions will be verified through two different types of tests, firstly by simulation and secondly by experiments with a laboratory prototype.

Numerical Investigation on Vibration Performance of an Improved Switched Reluctance Machine with Double Auxiliary Slots

Considerable vibration and acoustic noise limit the further application of Switched Reluctance Machine (SRM) due to its structural characteristics and working principle. An improved SRM model with double auxiliary slots (DAS) was proposed, in which the direction of the magnetic line of force was adjusted, and the radial magnetic density in the air gap was reduced by changing the local tooth profiles of the stator and the rotor. The effects of initial rotor position and turn-on angle and turn-off angle on radial Electromagnetic Force (EMF) and maximum torque were investigated. The results indicate the radial EMF and torque increase significantly with the advancement of the turn-on angle or the delay of the turn-off angle. In the orthogonal experimental design, initial rotor position, turn-on angle, and turn-off angle were taken as the factors, and the optimal set of parameters that minimized radial EMF was determined according to a greater output torque. In contrast to conventional SRM, the radial EMF of the SRM with DAS significantly reduces when the optimal set is applied.

IMPROVEMENT OF THE DESIGN ALGORITHM OF SWITCHED-RELUCTANCE MACHINES

The issue of improving the technical and economic indicators of switched-reluctance machines at the stage of their design has a significant degree of relevance. This study is devoted to improving the optimization algorithm for designing electric machines of the valve-inductor type. Parametric, single-criteria optimization was subject to consideration. The task of designing a magnetic system of a switched-reluctance machine is to find the optimal combination of values of geometric parameters, at which the value of the objective function reaches an extremum. Within the framework of this work, optimization was considered by the criterion of the minimum pulsations of the electromagnetic moment at low rotational speeds. The stochastic method – the Monte-Carlo method – was used as the basis for making changes to improve the efficiency of the optimization algorithm. The essence of the changes is to apply a normal distribution of a random variable with decreasing variance and with a variable value of the mathematical expectation instead of using a uniform distribution. For this study, methods of mathematical modeling were used, namely the Monte-Carlo method and methods of probability theory. Calculations of the magnetic field of the switched-reluctance machine were performed using the FEMM 4.2 program based on the finite element method. Due to the changes made to the basic optimization algorithm, the effectiveness of such a criterion as the time to achieve the final result with a given calculation accuracy has become higher. The obtained data can be practically useful in the development of manufacturing technology for the object of optimization.

Comparative Analysis of Dynamic Performance Between Switched Reluctance Motors 6x4 and 8x6

This paper presents a comparative study between the Switched Reluctance Machine (SRM) 8x6 and 6x4 operating as a motor with both 60kW of power. The computer simulation was performed in Matlab™ / Simulink® environment and allowed the machine behavior under various operating conditions to be verified. This work made it possible to evaluate: phase voltage and current, speed, torque and efficiency. Comparative results between the two machines will be presented and discussed.