Design and Control of a Bearingless Double U-Core Switched Reluctance Machine used for a Flywheel



Having “Switched Reluctance Machine” (SRM) with a flywheel simultaneously can present a lot of benefits including simple design, robustness of construction, and low idle losses due to the precious capabilities and additionally a cheap price which make this superiority more realistic by eliminating bearings in this research. They also offer the advantages of only providing positive currents and simplifying the inverter design. In the other side, the drawbacks of SRM machine can be eliminated in the presence of flywheel. The pulsating nature of torque (torque ripple) in SRM machine, acoustic noise and drag losses will be reduced owing to the presence of vacuum in flywheel.

The U-cores technology is naturally followed by a shorter flux paths than a regular SRM. Moreover, the change in position from unaligned to aligned is halved by doubling the number of poles. As a result, the amount of torque is doubled in the U-core SRM. On the other side, to overcome the problem of the U-core technology, which is the excessive amount of end windings, the double U-core technology was presented in which the number of U-cores is doubled and a coil is shared by the U-cores next to each other. However, the most important feature in using the double U-core technology in this research is the isolated coils which leads to have no coupling between them and the coils can be controlled individually with the hypothesis that it will be considered both as a machine but also a magnetic bearing.

The aim of this project is to develop the construction of a double U-core SRM in which the mechanical bearings are eliminated.

In this case, the stator windings plays a significant role in the machine. The windings of the machine should be used to stabilize the rotor in the center and create suspension of the rotor along with the torque generation. Therefore, calculating and optimizing the number of coils is essential in this respect.

A bearing may be required to stabilize the rotor against gravity (z-axis), which may also be a passive bearing in this plan. Furthermore, if the double U-core machine is separated into two stacks, more space is available for wiring and this issue will become more important if the rotor is suspended by a separate wiring on the stator.

To sum up, a precise model is needed to consider all the important details and parameters in the new structure of the double U-core SRM to achieve the goal of this project including machine design, flywheel design, dynamic model, control method, thermal argument, cooling system, material use and cost, to name but a few.

Funding: Self-financing and Department of Energy Technology, AAU.
Effektiv start/slut dato01/07/201831/12/2021


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