Investigation of the Temperature Effects on Copper Losses in Hairpin Windings
Round 1
Reviewer 1 Report
In this work, the focus was on ohmic losses in hairpin windings. The effects of both operating temperatures and rotor topologies were analysed in detail, using a surface mounted PMSM for race car applications as a case study.
Several points of criticism are now emerging:
- In general, it is a major disadvantage that this is only an analysis based on numerical simulations. Unfortunately, the results obtained have never been verified via an experimental approach. It is therefore not possible to verify whether the simulations carried out are correct. The publication loses considerable value as a result.
- It is not clear how high the temperature is in the steady state and how it was determined or fixed.
- In Table 2 it can be seen that the outer diameter of the new motor has become larger. What does this mean for the amount of copper used compared to the reference motor?
- Has the publication https://doi.org/10.3390/machines10050328 been observed?
- Unfortunately, the references are not in a consistent citation style.
- Some pictures are of poor quality. It is essential to work in vector format here.
Conclusion: A publication with a very interesting topic, but which suffers from the fact that there is no verification via an experimental approach.
Author Response
Dear Reviewer,
The authors appreciate the time taken by the Reviewers to read and review the paper in detail. For this, we would like to thank them. The comments have been mostly all taken on board. In general, we believe that the paper is now much clearer and significantly improved. We are also including a revised version of the paper with the modifications being highlighted.
Please see the attachment.
Sincerely,
The authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper summarizes the simulation results for AC copper loss in motors. There are some unclear points.
(1) Is Figure 1 the simulation result? Does the red part in Figure 1 indicate a high current density? The coil dimensions and conditions shown in the figure are also not shown. Please explain Fig. 1 in detail.
(2) Please explain the materials and detailed dimensions used for the motor shown in Fig. 2. What are the magnetic properties of permanent magnets and cores?
(3) Table 2; There is no definition of "kff" in the text.
(4) Table 2; How did you calculate the power density? Is the coil end (the part of the coil that protrudes axially from the stator core) considered? Why do the two motors have different power densities?
(5) Fig. 5; How is the AC power loss calculated by analysis? In addition, please explain the analysis conditions for magnetic field and heat.
(6) Fig. 7; What do you consider in the thermal circuit of the motor assumed in the thermal analysis? It is important to explain the analysis conditions because the results vary greatly depending on the analysis conditions.
(7) Fig. 7; The temperature rise value of the rotor magnet is quite high. Are permanent magnets affected by thermal demagnetization?
(8) This study is only the result of the conditions of the magnetic properties of one type of permanent magnet or core. How do different magnetic properties affect the conclusions of this paper?
(9) Fig. 10; Please explain the dimensions of each rotor topology.
(10) Fig. 11; The loss of permanent magnets in topologies 1 and 2 is very large. Is this the effect of suppressing spatial harmonics?
(11) Fig. 14; Since topology 3, 4 and 5 are embedded magnet type, I think that the current phases for obtaining the maximum torque are different. Are all the conditions in Figure 14 the same? Furthermore, is there any influence of heat from the iron core?
Author Response
Dear Reviewer,
The authors appreciate the time taken by the Reviewers to read and review the paper in detail. For this, we would like to thank them. The comments have been mostly all taken on board. In general, we believe that the paper is now much clearer and significantly improved. We are also including a revised version of the paper with the modifications being highlighted.
Please see the attachment.
Sincerely,
The authors
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The added changes increase the value of the paper. Unfortunately, it still suffers from the lack of an experimental approach to validate the simulation results. Nevertheless, I propose the paper for publication, as the readers will be aware of the shortcoming described.
Author Response
Thanks for having proposed the paper for publication. We are aware that the lack of experimental results is a shortcoming of the paper. We hope to provide an experimental verification in a future publication.
On the other hand, we would like to stress on that we strongly believe that the analysis is consistent and accurate, as FE models have been proven to be highly reliable in estimating electrical machine performance. As a research group, we work in the field of electrical machine modelling for a long time as proven by our publication records, and we have demonstrated the accuracy of analytical and FE models against experimental results in many previous publications. Therefore, we do believe that our findings are accurate. Additionally, most of the findings reported in the paper are based on comparative analyses and, as such, they are fair and consistent, although some discrepancies can appear when compared against experimental results. As mentioned above, we really hope to provide some experimental validation in future publications, but it is also true that we would need to prototype a number of machines and test them at different temperatures in order to prove all the findings of this paper. This is undoubtedly complex and expensive.
Thanks for all the suggestions provided during the review process.
Author Response File: Author Response.pdf
