Hybrid Switched Reluctance Motors for Electric Vehicle Applications with High Torque Capability without Permanent Magnet
, M. J. Hossain 1,*, Gang Lei 1, Premlal Ajikumar Sreelekha 2,*, Tibinmon Pulimoottil Monichan 2 and Sree Venkateswara Rao 3
Round 1
Reviewer 1 Report
Title: Hybrid Switched Reluctance Motors for Electric Vehicle Applications with High Torque Capability without Permanent Magnet
Journal: MDPI
Manuscript ID: energies-1960955
Comment 1: The most recent research in SRM is accomplished by enhancing the air gap flux density using permanent magnets (PMs) in the excitation system to provide greater electromagnetic torque. How this new topology enhances the torque capabilities of SRM without PM.
Comment 2: The simulation and experimental outcomes of this study are not stated clearly based on different characteristics such as torque, power density, speed range of the SRM.
Comment 3: How to boost the torque and power density of the SRM using hybrid excitation techniques.
Comment 4: Magnetic characteristics of two SRM's, the field line and flux distributions are varying from 0 to 2 tesla. But authors have not specified why these field and flux lines vary with aligned and unaligned poles.
Comment 5: In general, the section of Introduction is well organized, but lacks sufficient literature review. The introduction part should be improved further to review the relevant research and highlight the advantages of your work.
https://doi.org/10.1016/j.rser.2021.112038
https://doi.org/10.1002/er.8306
Comment 6: Static torque characteristics of HESRM under various currents with respect to the DC field injection are varied from 10A to 30A, it means that torque varies from minimum to maximum and finally reaches a minimum with the unaligned position. Authors can justify why this torque finally dropped to a minimum value?
Comment 7: Authors can include comparison between the static and dynamic characteristics of the SRM and HESRM results for better understanding and flow of the paper. Also, authors include variable speed control strategy for two SRMs, the speed ranges are not specified properly.
Comment 8: Avoid repeating words and sentences throughout the manuscript. Also, there is no flow continuity and readability, so can you rewrite the entire manuscript with continuity and readability?
Author Response
Answers to Reviewer 1 comments.
Comment 1: The most recent research in SRM is accomplished by enhancing the air gap flux density using permanent magnets (PMs) in the excitation system to provide greater electromagnetic torque. How this new topology enhances the torque capabilities of SRM without PM.
Answer: HESRM uses an auxiliary current along with the main current. Both these currents increase the flux inside the HESRM, thereby enhancing the torque. The auxiliary current replaces the PM used in conventional SRM. This is mentioned in lines 130 - 136.
Comment 2: The simulation and experimental outcomes of this study are not stated clearly based on different characteristics such as torque, power density, speed range of the SRM.
Answer: Graphs are included for the average torque, and the figure numbers are 16. We had limitations in taking characteristics of power density from experimental results.
Comment 3: How to boost the torque and power density of the SRM using hybrid excitation techniques.
Answer: This is briefly mentioned in "Machine Topology for the proposed machine". The torque and power density are increased by providing an auxiliary current to the motor.
Comment 4: Magnetic characteristics of two SRMs, the field line and flux distributions vary from 0 to 2 tesla. But authors have not specified why these field and flux lines vary with aligned and unaligned poles.
Answer: Since the SRM motor works on the reluctance principle, the field and flux lines vary with aligned and unaligned poles. This is explained in lines 197 - 204.
Comment 5: In general, the section Introduction is well organized but lacks sufficient literature review. The introduction should be improved further to review the relevant research and highlight the advantages of your work.
Answer: The proposed design's advantages are added in the Introduction - lines 87 - 96.
Comment 6: Static torque characteristics of HESRM under various currents with respect to the DC field injection are varied from 10A to 30A, which means that torque varies from minimum to maximum and finally reaches a minimum with the unaligned position. Authors can justify why this torque finally dropped to a minimum value?
Answer: Figure 7 denotes the static torque of the SRM according to the rotor position. To complete an electrical degree, the rotor travels from unaligned to aligned positions and back again. The static torque will vary in all these positions as the reluctance and inductive values changes. The aligned position has minimum reluctance and maximum inductance, increasing the air gap's flux density. Thus the middle portion of the graph will have maximum amplitude compared to the initial and final positions. This is explained in section 3.2.1.
Comment 7: Authors can include the comparison between the static and dynamic characteristics of the SRM and HESRM results for better understanding and flow of the paper. Also, the authors include variable speed control strategy for two SRMs, the speed ranges are not specified properly.
Answer: Studying speed control strategy is beyond this work's scope, and we plan to do this in future work. It is mentioned in conclusion (line 379).
Comment 8: Avoid repeating words and sentences throughout the manuscript. Also, there is no flow continuity and readability, so can you rewrite the entire manuscript with continuity and readability?
Answer: The entire article has been rewritten to improve readability.
Reviewer 2 Report
This paper studies a new topology to enhance the torque capability of HESRM without using PM or other rare earth components，and simulation and experiments show that the designed HESRM without PMs has a higher torque capability and efficiency than the conventional SRM. Here are some suggestions for the author:
(1) What is the difference between the proposed new motor topology and the traditional RSM? The description in this paper does not explain the specific differences, which can not be seen from Figure 1. It is suggested to clarify the differences in this paper.
(2) Figure 3 and Figure 4 cannot show the specific values of the magnetic density of the traditional SRM and HESRM. The 1.7-1.8T described in the paper can only describe a range, and the specific values are not clear. Compared with Figure 3 and Figure 4, HESRM's magnetic density is even smaller than SRM, so how does HESRM improve the electromagnetic torque? It is suggested to give a graph to make specific magnetic density values at different positions.
(3) In Section 3.3, it is suggested to give a concrete control block diagram including Simulink model, so that readers can quickly understand the control strategy of the motor.
(4) The current and torque curves in figure 8 are irregular, especially the current curves. Please explain the specific meaning of the curves at different moments in figure 8 and how they are obtained.
(5) In line 245, the author describes that the experimental results are consistent with the simulation results, but through comparison, it is found that the results in Figure 12 are different from the simulation results above. Why does the author say that the results of the two methods are consistent? Please explain the reason.
(6) This paper only makes a comparative analysis of HESRM without permanent magnet and traditional SRM, but does not reflect the difference between HESRM with permanent magnet in output performance. It is suggested to add this part.
(7) The curves and fonts of many figures in the paper are not clear, such as Figure 8, Figure 11, figure 12, etc. It is suggested to improve.
Author Response
Answers to Reviewer 2 comments.
Comment 1: What is the difference between the proposed new motor topology and the traditional RSM? The description in this paper does not explain the specific differences, which can not be seen from Figure 1. It is suggested to clarify the differences in this paper.
Answer: In conventional SRM, Permanent magnets vary speed and torque, whereas, in HESRM, we use additional DC to vary the torque and speed without using PM. This is explained using a block diagram in the paper and discussed under the "Machine Topology for the proposed machine "section.
Comment 2: Figure 3 and Figure 4 cannot show the specific values of the magnetic density of the traditional SRM and HESRM. The 1.7-1.8T described in the paper can only describe a range, and the specific values are unclear. Compared with Figure 3 and Figure 4, HESRM's magnetic density is more minor than SRM, so how does HESRM improve the electromagnetic torque? It is suggested to give a graph to make specific magnetic density values at different positions.
Answer: The steel material used in the conventional SRM for the simulation's maximum flux density range is 0-1.9T. In figure 3, the conventional SRM for the given excitation (5A) at the aligned position is 1.2 T and unaligned, reaching 1.6T.
In HESRM, in an aligned position with the same excitation current (5A), it reaches 1.06 T due to the unexcited pole of the auxiliary windings. In unaligned condition, 1.3T. The magnetic flux density improves with the help of an auxiliary injection current. This is explained in lines (144-155).
Comment 3: In Section 3.3, it is suggested to give a concrete control block diagram, including the Simulink model, so that readers can quickly understand the control strategy of the motor.
Answer: Control block diagram and detailed explanation are added. (Figure 3 ).
Comment 4: The current and torque curves in figure 8 are irregular, especially the current curves. Please explain the specific meaning of the curves at different moments in figure 8 and how they are obtained.
Answer: The graphs represent all three phase currents at different speeds. The irregularities in the phase currents are due to the speed changes since this motor is a three-phase switching machine. The longer switching patterns at the operation's beginning denote the motor's transient behaviour. The HESRM have two currents, main and auxiliary, respectively.
Comment 5: In line 245, the author describes that the experimental results are consistent with the simulation results, but through comparison, it is found that the results in Figure 12 are different from the simulation results above. Why does the author say that the results of the two methods are consistent? Please explain the reason.
Answer: Graphs have been added (Figures 13 and 14). The experiment was conducted for various torque and speed ranges, and the moving and instantaneous values were measured, including inverter and system efficiencies. The comparison between the conventional and proposed methods is specified precisely, whereas the graphs of the moving torque waveforms were misplaced. The updated waveforms have been replaced in the paper.
This graph shows the moving torque of the SRM at 1000 and 2000 rpm. The average torque of the conventional and hybrid SRMs differ by almost 1 Nm, shown in the figure. The conventional SRM reaches a maximum of 2 Nm, whereas the HESRM go up to 3. Since moving torque is measured, the maximal and minimal can go above and below the average value.
Comment 6: This paper only makes a comparative analysis of HESRM without a permanent magnet and traditional SRM but does not reflect the difference between HESRM with a permanent magnet in output performance. It is suggested to add this part.
Answer: The difference between HESRM with and without a permanent magnet in output performance is planned as future work.
Comment 7: The curves and fonts of many figures in the paper are not clear, such as Figure 8, Figure 11, figure 12, etc. It is suggested to improve.
Answer: Figures 8, 11 and 12 are improved and updated per request.
Round 2
Reviewer 1 Report
Accept
Reviewer 2 Report
The paper has been revised and improved according to the review comments.
