Induced EMF THD Reduction Design of Permanent Magnet Synchronous Generators for Diesel Engine Generators

Round 1

Reviewer 1 Report

A design method is proposed in this paper to reduce the total harmonic distortion (THD) of induced electromotive force (EMF) for the enhancement of power quality related to permanent magnet synchronous generator (PMSG). The selection process of the number of poles and slots for the initial design is given. The final design of the optimal rotor shape is studied using the eccentric curve and hole shape. The performance of the optimal rotor shape is verified through a 2-dimensional finite element analysis.

Some clarifications should be made before a possible publication:

1. At page 3 it is not clear how the figure 1 is obtained. Details are needed. Moreover, it is not clear how the data from Table 2 are obtained. Details are needed.
2. Concerning the Eq.(4), μ is not necessarily integer. It is not clear why the authors stated “where μ is a positive integer”.
3. At rows 219-225 are presented the components of the dq equivalent circuit, but the authors must mention also the system of differential equations which describes the connections between these components and governs the functioning of the whole PMSG.
4. More details are needed on how were obtained the figures 3,5,7,8,9,11,12 and 14

Author Response

Dear Reviewer,

Thank you for your kind and accurate comments form bottom of my mind.

I will describe the responses to your comments as following :

1. At page 3 it is not clear how the figure 1 is obtained. Details are needed. Moreover, it is not clear how the data from Table 2 are obtained. Details are needed.

I added the method of space harmonic analysis. Please, refer to the line 102 – 125 in the updated manuscript.

2. Concerning the Eq.(4), μ is not necessarily integer. It is not clear why the authors stated “where μ is a positive integer”.

I modify the definition of μ. Please, refer to the line 148-151 in the updated manuscript.

3. At rows 219-225 are presented the components of the dq equivalent circuit, but the authors must mention also the system of differential equations which describes the connections between these components and governs the functioning of the whole PMSG.

I add the process for the transformation from 3 phase to dq equivalent circuit. Please, refer to the line 255-279 in the updated manuscript.

4. More details are needed on how were obtained the figures 3,5,7,8,9,11,12 and 14.

The number of figure that reviewer commented has changed due to the modification by other reviewer comments as follows :

Figure 3 -> Figure 4, Figure 5 -> Figure 6, Figure 7 -> Figure 8, Figure 9 -> Figure 10, Figure 11 -> Figure 12, Figure 14 -> Figure 16

I wrote the obtained method for the changed number of figure above mentiond.

Figure 4 : Please, refer to the line 159-160 in the updated manuscript.

Figure 6 : Please, refer to the line 178 in the updated manuscript.

Figure 8 : Please, refer to the line 202 in the updated manuscript.

Figure 10 : The figures (a) and (b) in Figure 10 are the summarized results for Figure 7 and 9.

Figure 12 : The comparison of wave form and THD for the initial and final model is conducted by 2D FEA. The initial model corresponds to the Figure 3. The wave form and THD for the initial model are shown in Figure 4. The wave form and THD for the final model with the eccentricity 10mm are shown in Figure 8 (a) and Figure 10 (b). Therefore, The results of Figure 12 (a) and (b) come from the Figure 4, Figure 8 (a) and Figure 10 (b).

Figure 16 : The results of Figure 16 comes form Equation (10) – (13). Please, refert to the line 289-290.

Author Response File: Author Response.docx

Reviewer 2 Report

After the reading of the manuscript some comment arose:

• the title is quite complex to read, but it is just a comment.
• abstract is quite good and clear.
• the introduction lack of literature review and comparison: it is not clear what has been already proposed in the literature and why your proposal should sound compared to the existing solutions.
• line 54 the frequency is missing.
• measurement units are separated from the number. The same holds for the %.
• most of the choices made in Section 2 are not explained or justified, even in light of the other existing solutions.
• tables and pictures are good and readable
• the experimental part lacks of description in the results part. The final discussion is limited to a couple of lines of text.
• Again, results discussion and conclusion do not convince the reader about the novelties introduced by the authors and why it should be better than the existing (simply because no comparison has been made)

For those reason my suggestion is a major, pending the improvement of the lacking points.

Author Response

Dear Reviewer,

Thank you for your kind and accurate comments form bottom of my mind.

I will describe the responses to your comments as following :

1. the introduction lack of literature review and comparison: it is not clear what has been already proposed in the literature and why your proposal should sound compared to the existing solutions.

I listed the previous researches related to my research. I also described the weakness of previous researches compared to my research. Please, refer to the line 44-58.

2.measurement units are separated from the number. The same holds for the %. 

I modified all the measurement units of my updated manuscript in all pages.

3. most of the choices made in Section 2 are not explained or justified, even in light of the other existing solutions. 

As you commented, I added the selection process for my proposed design. Please, refer to the line 229-233.

4. tables and pictures are good and readable 

Thank you for your complements.

5. the experimental part lacks of description in the results part. The final discussion is limited to a couple of lines of text.

I added the difference between the results of 2D FEA and measurement. Please, refer to the line 341-344.

6. Again, results discussion and conclusion do not convince the reader about the novelties introduced by the authors and why it should be better than the existing (simply because no comparison has been made)

I added the core model specification, manufacturing method and installation of prototype in more details. Please, refer to the line 322-330.

I also added the novelties of my research compared to the previous researches. Please, refer to the line 369-376.

Author Response File: Author Response.docx

Reviewer 3 Report

The paper is dealing with design of permanent magnet synchronous generators for diesel engine generators. The focus is put on reduction of THD of induced EMF. The authors have introduced the scope and problem (which could be more in-depth and longer). Then the selection process for the number of poles and slots is described. Rotor shape design is proposed by using the eccentric curve and hole shape.Based on the results of the first process, the optimal rotor shape is selected to achieve the additional THD reduction of the induced EMF. Finally, the performance for the optimal rotor shape is verified through 2D FEA and a prototype experimental verification.

All in all, it is a standard procedure. There are no significant mistakes. The topic is important in electrical machine design, as the performance of the machines is expected to grow in energy efficient manners.

I would suggest the improving of Fig 16. The pictures are rather small. There are no differences in part b and c. Or the differences are too small to be seen in the pictures without guidance.

Highlighted texts in Fig 17b are rather small and hard to read. It must be improved.

Author Response

Dear Reviewer,

Thank you for your kind comments and suggestions from bottom of my mind.

I modified the manuscript as follows :

Suggestion 1

I would suggest the improving of Fig 16. The pictures are rather small. There are no differences in part b and c. Or the differences are too small to be seen in the pictures without guidance.

-> I emphasized the final rotor shape as shown in Figure 16 (b) of page 11.

     Please the attachment.

Suggestion 2

Highlighted texts in Fig 17b are rather small and hard to read. It must be improved.

-> I modified the measured wave form as shown in Figure 18 of page 12.

    Please see the attachment.

Reviewer 4 Report

Please note the following comments or suggestions:

1. Line 94: "In faction slot winding" may be "In fractional slot winding". Please check it.
2. Line 125: I think [16] can analyze air gap density but cannot calculate flux linkage. So, I suggest adding other literature that can calculate flux linkage.
3. Line 150 and Line 151: u in your assumption refers to permeability. So, u in (6) should be replaced by another symbol.
4. Line 154: Please check slot number,32 because there is not 32 in Table 2.
5. What does "PF 1" mean in Figure 13? Does it mean "PF=1" or "PF1". Please make it clear.
6. Line 379: Please check "it was".
7. Why not analyze the waveform of the induced EMF according to the slit, and compare the performance of the rotor shapes with eccentricity, slit, and eccentricity+slit?

Author Response

Dear Reviewer,

Thank you for your kind and accurate comments form bottom of my mind.

I will describe the responses to your comments as following :

1. Line 94: "In faction slot winding" may be "In fractional slot winding". Please check it.
I modified the adjective for "fractional" instead of faction. Please refer to the line 94 in the updated manuscript.
    
2. Line 125: I think [16] can analyze air gap density but cannot calculate flux linkage. So, I suggest adding other literature that can calculate flux linkage.
Yes, You are right. Reference [16] describes the analytic method of air gap flux density in the line 107, 115 and 119.
Reference [17] is added to analyze the induced EMF by using the flux linkage from space harmonic analysis. The above equation is described in Equation (46) in Reference [17].
            

3. Line 150 and Line 151: u in your assumption refers to permeability. So, u in (6) should be replaced by another symbol.
Thank you for your accurate comment. The symbol for the space harmonic order is modified as "r". Please refer to the line 148-151 in the updated manuscript.

4. Line 154: Please check slot number,32 because there is not 32 in Table 2.
Thank you for your accurate comment. The slot number is 30 instead of 32.Please refer to the line 154 in the updated manuscript.

5. What does "PF 1" mean in Figure 13? Does it mean "PF=1" or "PF1". Please make it clear.

Thank you for your accurate comment. I deleted space between PF and numerical value.
Please refer to Figure 13 in the updated manuscript. I also modified all Figures and sentence about your comment 5 in my manuscript.

6. Line 379: Please check "it was".
Thank you for your comment. I modified as you commented. Please refer to the line 379 in the updated manuscript. 

7. Why not analyze the waveform of the induced EMF according to the slit, and compare the performance of the rotor shapes with eccentricity, slit, and eccentricity+slit?
The rotor shape design with only the slit means that the value of eccentricity is 0 in Figure 10. Therefore, The slit shape with the eccentricity 0mm has higher THD than the eccentricity and eccentricity+slit shape.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Some of the comments have been addressed, others not as much as i thought.

The main weakness is the lack of quantitative results and their description. E.g.: The results in Table 6 do not convince the reader that the proposed method is worth to be implemented.

Author Response

Dear Reivewer,

Thank you for your kind comment.

I will reply to your comment as follows :

1. Some of the comments have been addressed, others not as much as i thought.

The main weakness is the lack of quantitative results and their description. E.g.: The results in Table 6 do not convince the reader that the proposed method is worth to be implemented.

As you know, Table 6 means the results for the 2D FEA of proposed design and its prototype measurement. The design results of proposed design are shown in Figure 11. Generally, the error percentage of induced emf for the design specification and its prototype is within 5%. This allowed regulation percentage 5 % for the induced emf of prototype is widely accepted in the manufacturer of electric machinery. Therefore, my research result meets this requirement as described in the line 340 on page 13. This percentage value is not a standard value. So, any companies of electric machinery do not open the performance variation value of electric machinery including the above percentage value in public. So, I do not describe these situations in my manuscript. Please, understand these situations.

Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

I leave the decision to the editors

Author Response

Dear Reviewer,

I submit the modified manuscript which was proofread by native english editor.

Thank you for your kind and accurate comments from bottom of mind.

Sincerely,

Author Response File: Author Response.docx