Abstract
With their highly robust nature and simple design, switched reluctance machines are finding their way into numerous modern day applications. However, they produce oscillatory torque that generates torque ripple and mechanical vibrations. A double rotor structure to maximize the flux linkage and thereby increase the torque generating capability is proposed. As the machine operates close to saturation, the torque computation depends heavily on the energy conversion as the rotor rolls over the stator for a fixed pole pitch. The flux linkage characteristics are highly non-linear, hence estimation of the magnetic and mechanical parameters is extremely cumbersome. Magnetic circuit analysis by interpretation of the number of flux tubes using integration techniques at different positions of the machine to develop the flux linkage characteristics of the double rotor structure is presented. Computation of the inductances during the movement of rotor from unaligned to aligned is crucial in determining the generated torque. Relevant equations of calculations for inductance and flux linkages in the aligned, partially aligned and unaligned positions are computed. The partially aligned computation is based on the average on two intermediate positions, namely the 1/4th aligned and 3/4th aligned conditions. The static torque characteristics based on the energy conversion principles are used to compute the torque value. Results from simulation and experiments used for performance evaluation of the proposed flux tube analysis for computation of the electro-magnetic torque are presented.
Highlights
Switched Reluctance Motors (SRMs), due to their simple structure, are finding their way to replace industrial and commercial induction machines in a major equipment overhaul
A comparative evaluation of the computational results from the flux tube analysis is performed with the results derived using standard FEM tools and the measurement results from the prototype setup under laboratory conditions
The flux path is categorized as three parallel tubes with the end flux tubes interchanging the flux pattern at the other end of the stator pole with the center flux tube having a uniform flux flow for any intermediate position
Summary
Switched Reluctance Motors (SRMs), due to their simple structure, are finding their way to replace industrial and commercial induction machines in a major equipment overhaul. The reduction of the air-gap in the mechanical structure introduces an increased radial pull due to the strong flux lines, resulting in the generation of torque ripple To overcome this effect a Double Rotor Reluctance Motor (DRSRM) was developed [2], exploiting the fact that with the same excitation a dual series magnetic path is established at the interface of the stator—rotor teeth, thereby increasing the torque generating capability. The electro-magnetic approach using flux tube analysis is proposed and the flux linkage values derived from the energy equations are used to predict the electromagnetic torque characteristics of the machine. In comparison with all the flux tube computation methods mentioned above, our proposed magnetically equivalent circuit method involves assumption of three main flux tubes in a partially aligned condition and two. A comparative evaluation of the computational results from the flux tube analysis is performed with the results derived using standard FEM tools and the measurement results from the prototype setup under laboratory conditions
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