Browsing by Author "Pittam, P.K."

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Efficiency improvement and torque ripple minimisation of four-phase switched reluctance motor drive using new direct torque control strategy
(Institution of Engineering and Technology kvukmirovic@theiet.org, 2020) Pittam, P.K.; Ronanki, D.; Parthiban, P.
The direct torque control (DTC) strategy is one of the most effective techniques, used to control the switched reluctance motor (SRM) with improved dynamic performance and reduced torque ripple. However, this approach draws a higher source current due to an extension of the phase current into the negative torque region, which lowers the net torque per ampere ratio. This study proposes a new DTC strategy for SRM to overcome this issue by modifying the partition of the sectors and appropriate voltage vector selection. Therefore, the proposed method improves the drive efficiency while minimising torque ripple. To implement this method, a non-linear machine model is developed using the torque and flux characteristics obtained from experimental studies on a four-phase 8/6 SRM. The proposed DTC scheme is implemented on a digital control platform and power loss calculations are performed to evaluate the drive efficiency. Test results show that the proposed DTC method has improved performance in terms of efficiency and torque ripple under various operating conditions in comparison to the conventional DTC strategy. © The Institution of Engineering and Technology 2019.
Selection of electric drive for EVs with emphasis on switched reluctance motor
(CRC Press, 2023) Pittam, P.K.; Parthiban, P.; Kalpana, R.
Different electrical machines have been investigated to check their suitability for electric vehicle (EV) applications. The interior permanent magnet synchronous motor (IPMSM) and brushless DC (BLDC) motor are widely employed in EVs due to the use of permanent magnets (PMs), which provide high torque density and better efficiency. Therefore, PM machines are the preferred choice for applications where a high-efficiency motor is required. However, manufacturers are interested in finding an alternative to PM machines to avoid the issues related to rare-earth magnets. Induction machines (IMs), switched reluctance machines (SRMs) and synchronous reluctance machines (SyncRels) are gaining importance for EVs due to the lack of PMs. The simple and low-cost construction due to lack of PMs or windings on the rotor makes the SRM a potential candidate for EV applications in preference to PM machines and IMs. SRMs are more reliable in high-speed and high-temperature operation due to the absence of rotor excitation. The price volatility, environmental concerns and supply chain issues of rare-earth magnets present in PM machines have become a long-running problem in producing high-efficiency motors [1]. However, the absence of rare-earth magnets in SRMs is an advantage in this aspect. Rotor displacement and rotational stress limit the performance of PM motors in high-speed operation due to excessive centrifugal forces, which cause stress to develop in magnet slots and bridges. However, SRMs can be operated at high speeds due to the lack of slots and bridges in the rotor. The performance of PM machines deteriorates during field-weakening operation, whereas in SRMs, field weakening is a natural phenomenon at high speed. Moreover, SRMs have a wide constant power-speed range compared with PMs and IMs. IMs suffer from rotor copper losses due to the use of die-casting aluminium for rotor conductors, which limits high-temperature operation; usually, copper die-casting is used at high temperature, and this involves an expensive and challenging manufacturing process. Moreover, the independent torque production capability of each phase due to the electrical isolation of each phase endows SRMs with a fault-tolerant nature. In spite of all these advantages, SRMs suffer from high torque ripple, noise and vibration. However, torque ripple doesn't exclude the adaption of SRMs for EV applications; several significant contributions have been made towards torque ripple minimization by modifying rotor geometry and optimized control of phase current. The selection of the electric drive is the crucial step of EV design. This chapter deals with selection criteria and a comprehensive understanding of performance characteristics of different electric drives widely used in EV applications, including PM machines, IMs and SRMs. This chapter mainly deals with how the control principles have been evolved for SRMs to meet the requirements of EV adaption and briefly discusses the control methods established for performance enhancement, such as torque ripple minimization and torque to ampere ratio improvement. This chapter also deals with the adaption of direct torque control (DTC) to SRMs and analyses the reasons behind negative torque generation in phase. This chapter includes recent contributions towards the evolution of DTC over a period of time in terms of sector reorganization, voltage vector reformation and optimized voltage vector selection. This chapter also presents simulation studies of conventional and modified versions of DTC. © 2023 selection and editorial matter, Dharavath Kishan, Ramani Kannan, B Dastagiri Reddy and Prajof Prabhakaran; individual chapters, the contributors.
Torque Ripple Minimization of Four-phase Switched Reluctance Motor using Direct Torque Control with an Innovative Switching Sequence Scheme
(Institute of Electrical and Electronics Engineers Inc., 2019) Pittam, P.K.; Ronanki, D.; Parthiban, P.; Beig, A.R.; Williamson, S.S.
Direct torque control (DTC) technique is the prominent control strategy, used to control the switched reluctance motor (SRM) with a reduced torque ripple in comparison to the traditional current control techniques. However, it draws higher phase current in order to maintain the required electromagnetic torque during phase commutation, thus reduces torque per ampere. To circumvent this issue, a new DTC method with an innovative switching sequence is introduced in this paper, which minimizes torque ripple as well as power loss. The efficacy of the proposed scheme is validated for four-phase SRM through detailed simulation studies and compared with the conventional DTC scheme. The results show that the proposed scheme exhibits an improved steady-state as well as dynamic performance under various operating conditions. Â© 2019 IEEE.