Experimental Tests on a Spoke-Type Permanent Magnets Synchronous Machine for Light Electric Vehicle Application
, Marius Dranca, Mihai Chirca, Alexandru-Madalin Pacuraru, Petre-Dorel Teodosescu and Claudiu-Alexandru OpreaRound 1
Reviewer 1 Report
This study investigated the experimental testing of spoke-type PMSM that was developed based on the requirements of the L6e European light vehicle class. An accurate estimation of the PMSM-based E-drivetrain performance was also obtained by implementing The Worldwide Harmonized Light-Duty Vehicles Test Procedure on the control stage of the testing set-up. This work provides insight into the efficiency of the entire drive system (battery –inverter – PMSM) and the autonomy of the L6e light EV. I would like to recommend its publication if the authors can clarify the following concerns:
- The results shown in this manuscript need to be compared with previous findings so that the readers can understand the significance and novelty of this manuscript. It would be highly desirable if the authors can list a table to clarify this.
- In Table 2, there is some difference between simulation results and experimental results. What is the reason behind this?
Author Response
Dear Reviewer, thank you for the observations and appreciations. Following, please find our responses:
- A new section was added in the Conclusion section of the paper, highlighting the main contributions of the work:
“The main novelty of the article consists in the presentation of a full development process of a drive train for light electric vehicle, specifically the L6e European class. Although similar PMSM structures, using ferrite magnets, were previously investigated in literature, this paper provides a guideline for a full development process, beginning with the requirements, going through the lengthy design – simulation – optimization – prototyping – testing process and finally validating the procedure by integrating the drive train on a light EV and testing the prototype in real-life conditions.”
The recommendation to compare the results to previous work in the literature was addressed, but we did not find studies focused in L6e light electric vehicles or on similar spoke-type PMSM using rare-earth materials. Considering this, a comparison of the performances of the machines was considered to be inaccurate.
- The difference between the simulation and experimental results was explained in text (page 6): “A good correlation between the measured and estimated values can be noticed, the most notable difference is for the motor phase resistance, where the FEM-computed value is 24.3 % smaller than the measured value, since in the simulations only the active part or the windings was considered, without considering the connections to the terminals and longer end-windings. The differences between the other three electrical parameters (measured versus FEM-computed) can be explained by the fact that the manufactured machine could not be built exactly like the machine considered in simulations: different airgap length, different materials (PMs, iron core) properties, etc.”
Reviewer 2 Report
The authors use Interior Permanent Magnet PMSM and the Spoke-type PMSM for driving light mechanical vehicles.
The disadvantage of this paper is the lack of novelty. The authors use the well-known construction of permanent magnets PMSM. As a minimum element of the novelty, the comparison of two magnet variants (internal permanent magnet PMSM and PMSM of the spoke type) can be considered. This paper could be accepted if the authors add results of measurement of movement dynamic.
The paper in this form shouldn’t be accepted for Applied Sciences.
Author Response
Dear Reviewer, thank you for the time taken to read our paper proposal and for the proposals made.
To address the observation regarding the lack of novelty, a new section was added in the Conclusion section of the paper, highlighting the main contributions of the work:
“The main novelty of the article consists in the presentation of a full development process of a drive train for light electric vehicle, specifically the L6e European class. Although similar PMSM structures, using ferrite magnets, were previously investigated in literature, this paper provides a guideline for a full development process, beginning with the requirements, going through the lengthy design – simulation – optimization – prototyping – testing process and finally validating the procedure by integrating the drive train on a light EV and testing the prototype in real-life conditions.”
Also, our review of existing studies on development of drivetrains for light electric vehicles did not identify similar approaches for this type of EV (L6e class). Some papers on the topic were found, but in different power and speed ranges. In the same time, these studies were focused on ferrite-PMSM with 8 or 10 poles, so the performances could not be currently compared.
Previous work of the authors, cited in this paper, included a more detailed comparison between the two PMSM structures. The current work is focused on the entire design – integration cycle, which was only finalized for the spoke-type PMSM.
Your suggestion of presenting measurements of movement dynamic would indeed increase the value of the study. Unfortunately the PMSM drive train was integrated in a L6e prototype that is not public road-homologated, so very limited tests could be performed, mainly to determine that the required specifications are met. Dynamometer testing could prove more accurate in replicating the WLTP drive cycle, but that was not available for our team during testing.
Reviewer 3 Report
The paper deals with experimental tests on a spoke-type permanent magnets synchronous machine for light electric vehicle application. Types of motors considered in the paper are well known. The novelty of the paper should be highlighted.
The efficiency map is built for two considered motors. Please, add them to the paper.
The motors were optimized with GA. Describe the procedure. Which are the optimization goals?
Provide additional information on the motors’ windings. Are they distributed two-layer windings? Usually, in a distributed winding, there are upper and down layers, not left and right one.
Show d and q axes in Fig. 2.
Author Response
Dear Reviewer, thank you for the observations! Following, please find our responses:
- A new section was added in the Conclusion section of the paper, highlighting the main contributions of the work:
“The main novelty of the article consists in the presentation of a full development process of a drive train for light electric vehicle, specifically the L6e European class. Although similar PMSM structures, using ferrite magnets, were previously investigated in literature, this paper provides a guideline for a full development process, beginning with the requirements, going through the lengthy design – simulation – optimization – prototyping – testing process and finally validating the procedure by integrating the drive train on a light EV and testing the prototype in real-life conditions.”
- The efficiency maps were added in Appendix A, Figure A1.
- The optimization procedure was described in pages 3 and 4.
- Additional information was provided in page 3, confirming your assumption.
- d and q axes were shown in Fig. 2.
Reviewer 4 Report
This paper is very well done, well structured and answers the journal's theme.
However I advise the author to rectify the comments that I presented throughout the paper, then to update them.
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer, thank you for your observations and appreciations. Please find bellow the response for each of your recommendations:
L20 – the keywords were alphabetically ordered
L127 – A “.” was added at the end of the table title
L151 – A “.” was added at the end of the table title
L270 – Conclusions:
To address the observation regarding the lack of novelty, a new section was added in the Conclusion section of the paper, highlighting the main contributions of the work:
“The main novelty of the article consists in the presentation of a full development process of a drive train for light electric vehicle, specifically the L6e European class. Although similar PMSM structures, using ferrite magnets, were previously investigated in literature, this paper provides a guideline for a full development process, beginning with the requirements, going through the lengthy design – simulation – optimization – prototyping – testing process and finally validating the procedure by integrating the drive train on a light EV and testing the prototype in real-life conditions.”
Our review of existing studies on development of drivetrains for light electric vehicles did not identify similar approaches for this type of EV (L6e class). Some papers on the topic were found, but in different power and speed ranges. In the same time, these studies were focused on ferrite-PMSM with 8 or 10 poles, so the performances could not be currently compared. Two new references were added, presenting studies on spoke-type PMSMs.
Previous work of the authors, cited in this paper, included a more detailed comparison between the two PMSM structures. The current work is focused on the entire design – integration cycle, which was only finalized for the spoke-type PMSM.
Round 2
Reviewer 2 Report
The authors have improved their work. It can be accepted as it is.
Author Response
Thank you for your appreciation!
Reviewer 3 Report
I have still not understood your winding. Some slots are filled with the same color. Does it mean that there is the same phase in the slot? In such slots, there are symbols pointing out opposite signs.
What is the power of the converter required?
Author Response
Dear reviewer, thank you for the close look on our windings distribution (Fig. 2). Indeed, there was a mistake in some slots with the symbols of "in" and "out". Sorry for this error. We have corrected it. Please find attached the article with the corrected Fig. 2. And yes, some slots accommodate the same phase.
Regarding your second question, the required converter power is 7 kW, as the maximum permitted mechanical power (for L6e class electric vehicles) is 6kW, the difference will cover the electrical and mechanical losses. This is valid if unitary power factor PMSM control in implemented. If not, a small increase in converter power is required, depending in the lowest power factor during operation.
Author Response File: 
Author Response.docx
