Review Reports - Research on Combinations of Stator Poles and Rotor Teeth for Conventional Flux-Switching Brushless Machines with Composite Phase Numbers

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors propose a methodology to deduce stator-rotor combinations of machines with composite phases. Six, nine, twelve and four-phase conventional machines are derived. The topic of multi-phase machines has recently gained increased interest.

There are already published research works that have focused on this topic. Some of them already explored the possibility of obtaining multiple three-phase machines from 6, 9 and 12 phase machines. For example:

S. Abdel-Khalik, A. M. Massoud and S. Ahmed, "Application of Standard Three-Phase Stator Frames in Prime Phase Order Multiphase Machine Construction," in IEEE Transactions on Industrial Electronics, vol. 66, no. 4, pp. 2506-2517, April 2019, doi: 10.1109/TIE.2018.2840497.
Bianchi and M. Dai, "Use of the star of slots in designing fractional-slot single-layer synchronous motors", IEE Proceedings - Electric Power Applications, Volume 153, Issue 3, 2006. https://doi.org/10.1049/ip-epa:20050284

Therefore, my main concern regarding this paper is related to its novelty. While I believe that this paper does a good job of summarizing multiple ways to convert between composite phase numbers, I do not know if the novelty is enough for publication.

Besides this concern, the paper is well structured and written, with few misspells.

Regarding the results shown in this paper, it is not clear if they were obtained through simulation or experimentally (Figures 5b, 7b, 10b, 12, 13, 14, and 15). Therefore, more information should be provided about the simulation models, or the experimental results.

In section 4, please provide the rated values for the standard 6-phase machine.

There are some subjective words that should be changed. For example “pretty” in line 150, and “bigger” in 301.

Author Response

Dear Reviewers:

Thank you for your careful reading and comments concerning our manuscript electronics-3736574 entitled “Research on Combinations of Stator Poles and Rotor Teeth for Conventional Flux-Switching Brushless Machines with Composite Phase Numbers”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research.

We have studied the comments carefully and have made corrections which we hope meet with approval.

Attached please find our responses to the reviewers’ comments one by one.

Best wishes,

Guishu Zhao

on behalf of the authors

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper establishes statistical rules for the design of the phase number extension of the existing FSPM and compares and analyzes the electromagnetic performance. It is well-structured overall.

However, the following improvements are needed to increase the academic completeness and submission possibility:

Clarification of the purpose and contribution of the paper is needed

The introduction and abstract focus on the derivation of the “composite phase number” design rule and the exemplary performance comparison, but it is not clear what differences this study provides from the existing literature or what generalized design rules it provides.

In the introduction or conclusion, emphasize that “previous studies were focused on numerical examples, but this study suggests the possibility of extension with a general formula-based approach.”

Strengthening the interpretation of the electromagnetic advantage of the dual-phase structure is needed

The performance difference (Back-EMF, Torque, Inductance) between the standard six-phase and dual three-phase of the 24/22 structure is limited to a numerical comparison, and the analysis of the underlying principles is weak.

If the cause of the EMF increase is the difference in winding factor, the geometric structure or the analytical explanation of the magnetic flux path should be reinforced. Since the possibility of fault-tolerance degradation due to the increase in mutual inductance is only mentioned conceptually without actual fault model simulation, the persuasiveness is increased if the behavior change when a fault occurs in the time domain is supplemented with simple simulation results.

Lack of mention of the scalability of the proposed generalized model

Although the conclusion states that it is "scalable to E-core, C-core, and single-layer winding structures," there are no practical application examples or precautions for application.

Therefore, in order to emphasize that this paper is not limited to 'traditional FSPM', a brief mention is needed, for example, 'How does the definition of q′ change in the E-core structure?' or 'How does the K value change when the winding is single-layered?'

Updating and specifying the references is absolutely necessary.

Some of the key literature is more than 10 years old and lacks perspectives compared to recent papers. Therefore, it is necessary to add recent papers and significantly supplement background studies to establish its position in the current research flow.

Author Response

Dear Reviewers:

We have studied the comments carefully and have made corrections which we hope meet with approval.

Attached please find our responses to the reviewers’ comments one by one.

Best wishes,

Guishu Zhao

on behalf of the authors

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In the paper, the method of determining the stator-rotor combinations of conventional FSPM machines with composite phases (four, six, nine, and twelve phases) is presented, starting from machines with classical two-phase or three-phase windings.

An essential merit of the authors is that they draw a parallel between standard machines with four, six, nine, or twelve phases and asymmetrical two- or three-phase ones. Additionally, the stator/rotor pole combinations of conventional FSPM machines with composite phase numbers, along with their corresponding winding factors, are calculated.

To the authors:

Why don't you refer to coils marked with prime indices (like 2') in the text, and do these notations appear in the figures? It would be commendable if the notations were the same in both the text and the figures, explaining what the indices mean!
In Figure 14, the authors refer to the electromagnetic torque of the motor, specifying only the current density, not the current value! Additionally, it is unknown what type of permanent magnets the motor uses, so the absolute values of the torque are meaningless.
When comparing a multiphase machine with a dual three-phase or four three-phase machine, the authors do not discuss the control mode of the latter at all. Does the control method of the machine (dual three-phase, four three-phase, etc.) affect the obtained results? If so, I suggest explaining how the machine is controlled.
Fig.15 shows the value of the inductances. How were these values determined? Are they dependent on the current value? If yes, have they been determined in the same conditions?

Author Response

Dear Reviewers:

We have studied the comments carefully and have made corrections which we hope meet with approval.

Attached please find our responses to the reviewers’ comments one by one.

Best wishes,

Guishu Zhao

on behalf of the authors

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

- The number of references is too small. The number of references should be at least 25. The references are from the years 2005-2016.

- Equations 1 to 11 are not numbered.

- Line 38 Four-phase 16/12 (16-stator-poles/12-rotor-teeth), For the relations from line 50 Pr=Psc±K=Ps±K, where Pr, Ps, and Psc are respectively the number of rotor poles, stator teeth, and stator coils, and K is the number of coil-pairs having 51 complementarity. On line 50 define Pr the number of rotor poles and Ps the number of stator teeth. Please correct these notations. Please number the equation from line 50.

- The topicality of this work is not clear. The authors' contributions are not clearly presented.

- In Section 2, conventional six-, nine-, twelve-, and four-phase FSPM machines are presented to determine how composite-phase machines are derived from prime-phase machines. It would be sufficient to present only 2 types of machines because in Section 4 a comparison is made between the standard six-phase 24/22 machine (symmetrical topology) and the three-phase dual 24/22 machine (asymmetrical topology).

- In Section 3, no references are given for the equations used to determine the winding factors of composite-phase machines.

- For the prototype in Fig. 5.a, please specify how the EMF waveforms for the 6 phases were obtained. Please complete a table with the key design parameters of the FPSM machine in the text (see ref. 10)

- The prototype in Fig. 7.a, Nine-phase 36/34 FSPM machine, was presented in ref.10. Fig. 7.b is not clear. Please specify how the EMF waveforms for phases A1, B1, and C1 were determined. Were the EMF waveforms for the 3 phases measured in no-load? Please specify the motor speed at which the EMF voltages were measured.

- Please specify the reference for the prototype in Fig. 10.a and how the EMF waveforms in Fig. 10.b were determined. The graph in Fig. 10.b is not clear.

- Please provide a prototype for the four-phase FSPM machine as well.

- Please provide a separate table for the fundamental and third harmonic winding factors of the dual three-phase machine and the standard machine.

- Please specify what was represented in Fig. 12.b.

- Please specify whether you have made the prototype for the standard six-phase and dual three-phase 24/22 machines or if you have studied the two types of machines only by the finite element method (FEM).

- The conclusions are not accompanied by results.

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

Dear Reviewers:

We have studied the comments carefully and have made corrections which we hope meet with approval.

Attached please find our responses to the reviewers’ comments one by one.

Best wishes,

Guishu Zhao

on behalf of the authors

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for the clarifications and improvements on the manuscript.

Regarding FEA simulations, please provide some useful information about them. For example, which formulations were used? Were they done time-dependent or parametric stationary? Mesh used? Material properties (iron core saturation?).

Best regards

Author Response

Dear Reviewers:

We have studied the comments carefully and have made corrections which we hope meet with approval.

Attached please find our responses to the reviewers’ comments one by one.

Best wishes,

Guishu Zhao

on behalf of the authors

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have faithfully addressed the reviewers' requests for improvements.

Author Response

Dear Reviewers:

Thank you very much for your time and valuable feedback during the review process. We truly appreciate your recognition of our efforts to address the previous comments. We will continue to refine the manuscript with great care to meet the standards of the journal.

Best wishes,

Guishu Zhao

on behalf of the authors