Temperature Rise Calculation of the High Speed Magnetic Suspension Motor Based on Bidirectional Electromagnetic–Thermal–Fluid Coupling Analysis
Round 1
Reviewer 1 Report
In this paper, the loss and temperature rise characteristics of magnetic suspension high speed motor are studied. In order to accurately analyze the temperature distribution, a multi-physical coupling method including flow field, electromagnetic field and temperature field is proposed. The temperature distribution of the motor under different operation conditions is analyzed by using two different temperature rise calculation methods and compared with the measured results. It was found that the results of the multi-field coupling simulation are more consistent with the experiment, which verifies the superiority of the proposed analysis method.
The results are original and important. The proposed method could improve the analysis accuracy of motor loss and temperature rise and to predict more accurately the temperature rise in the motor design stage.
I have the following comments:
Line 74: please provide full description for CFD acronym.
Figure 2 shows the 2D grid of electromagnetic field analysis. It would be good to have scale on the graph, not only explanation in the text.
Fig 5: to have the scale would be more convenient.
Fig 6 It is difficult to read the text (too small font) in the figures
The manuscript presents many graphical results with different data, however, I missed in the text more detailed analysis of the obtained graphical results summarizing the main points which are mostly important for the analysis of the motor.
Conclusions are clear enough; however, it would be good to give some recommendations how to use the presented model in reality.
Author Response
Thank you very much for your valuable comments. According to your suggestions, we add much deeper discussions and appropriated modifications. In the following, a detailed point-by-point response for all comments 1-6 are provided. For details, Please see the attachment.
Comment 1: Line 74: please provide full description for CFD acronym.
Response: Thank you very much for your valuable advice. Full description of CFD has been added. (Please see section “1. Introduction”, second paragraph.)
Comment 2: Figure2 shows the 2D grid of electromagnetic field analysis. It would be good to have scale on the graph, not only explanation in the text.
Response: Thank you very much for your advice. We have added scale at the bottom of the image to make it more intuitive. (please see section “2.3.1 Meshing and Boundary Conditions”, Figure 2.)
Comment 3: Fig 5: to have the scale would be more convenient.
Response: Thank you very much for your advice. We have added scale at the bottom of the image to make it more intuitive. (please see section “2.3.2 Calculation of Heat Source of Electromagnetic Field”, Figure 5.)
Comment 4: Fig 6 It is difficult to read the text (too small font) in the figures.
Response: Thank you very much for your advice. We ignored the problem and have revised the picture. (please see section “2.3.3 Calculation of Cooling Conditions for Flow Field”, Figure 6.)
Comment 5: The manuscript presents many graphical results with different data, however, I missed in the text more detailed analysis of the obtained graphical results summarizing the main points which are mostly important for the analysis of the motor.
Response: Thank you very much for your comments. After careful analysis, we modified the last part of the result analysis. The two thermal analysis methods are compared with the experimental results, which can show the accuracy of the coupling method more directly. (please see section “3.3 Experimental Verification”, second paragraph and Figure 14.)
Comment 6: Conclusions are clear enough; however, it would be good to give some recommendations how to use the presented model in reality.
Response: Thank you very much for your comments. The structure of different motors is slightly different, but the structure of the magnetic levitation high-speed high-power motor used in this paper is very complicated, so the analysis is the most difficult. So for ordinary low speed motors, the analysis results will be more accurate. In addition, in order to verify the applicability of this method under different working conditions, we carried out an analysis in “3.2 Temperature rise analysis under different working conditions”
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper presents an interesting study on the simulation of the temperature rise of a high speed motor based on a multi-field coupling method. The results can be helpful in improving the accuracy of the temperature rise and motor loss analysis, even during the design stage. While the research design is properly described and the simulation model is duly described, some of the methods and parameters need more accuracy in their description, as follows:
1. When describing the boundary conditions of the simulation model the authors choose to ignore the influence of radiation heat transfer. However, in dynamic conditions of operation of the motor, the external motor housing can be in the vicinity of other heat radiating parts. Would it be possible to comment of the potential results of the simulation if the radiation heat transfer IS taken into account?
2. Figure 14: it is said that "The winding error is 6%, which is derived from the equivalent of the winding, but the above errors are within the allowable range, and the error between the overall experimental results and the simulation results is less than 10℃". First, the authors must precise the method of estimating the errors, on each of the 4 positions of the temperature sensors. Second, the authors must precise what errors are they calculating: the root mean square, mean absolute error, do the estimation takes into account both the systematic and the random errors or not. Third, the estimation of the errors is a criterion of the advantages (superiority) of the multi-field coupling simulation model over other existing simulation models. Some indication regarding the errors given by other simulation models (thermal analysis), previously published, would be thus more than beneficial.
Providing these issues are properly addressed the paper can be considered for publication in Machines.
Author Response
Thank you very much for your valuable comments. According to your suggestions, we add much deeper discussions and appropriated modifications. In the following, a detailed point-by-point response for all comments 1-2 are provided. For details,please see the attachment.
Comment 1: When describing the boundary conditions of the simulation model the authors choose to ignore the influence of radiation heat transfer. However, in dynamic conditions of operation of the motor, the external motor housing can be in the vicinity of other heat radiating parts. Would it be possible to comment of the potential results of the simulation if the radiation heat transfer IS taken into account?
Response: Thank you very much for your advice. We've thought about this before. But because the motor housing itself will not reach a very high temperature, there is no need to pay attention to the temperature of the motor housing when designing the motor. We have analyzed that for magnetic suspension motor, because the rotor does not contact the stator, the temperature of the rotor is not affected by the temperature of the stator. Motor housing temperature is not the focus of this paper, so the influence of radiation heat transfer is ignored in the analysis
Comment 2: Figure 14: it is said that "The winding error is 6%, which is derived from the equivalent of the winding, but the above errors are within the allowable range, and the error between the overall experimental results and the simulation results is less than 10℃". First, the authors must precise the method of estimating the errors, on each of the 4 positions of the temperature sensors. Second, the authors must precise what errors are they calculating: the root mean square, mean absolute error, do the estimation takes into account both the systematic and the random errors or not. Third, the estimation of the errors is a criterion of the advantages (superiority) of the multi-field coupling simulation model over other existing simulation models. Some indication regarding the errors given by other simulation models (thermal analysis), previously published, would be thus more than beneficial.
Response: (1) Thank you very much for your advice. First of all, the error of the winding is not 6% but 6℃, which is the result of the comparison between experiment and simulation. There is a mistake in writing; (2) The experimental result is the average value obtained by us through 6 tests and then compared with the simulation result for analysis; (3) According to your opinion, we have compared the two analysis methods with the experimental results respectively. (please see section “3.3. Experimental Verification”, second paragraph and Figure 14.)
Author Response File: 
Author Response.pdf
Reviewer 3 Report
I suggest the authors consider the following points in order to improve the paper:
The abstract of the paper is unorganized and logically incoherent.
Please name the main components of motor in Figures 1 and 13.
Please describe the measuring elements of the test stand.
How was the air friction loss determined (Figure 8). Please provide formula.
Author Response
Thank you very much for your valuable comments. According to your suggestions, we add much deeper discussions and appropriated modifications. In the following, a detailed point-by-point response for all comments 1-4 are provided.For details, Please see the attachment.
Comment 1: The abstract of the paper is unorganized and logically incoherent.
Response: Thank you very much for your suggestion. According to your opinion, we have carefully modified the abstract of the paper, which can be seen in the abstract
Comment 2: Please name the main components of motor in Figures 1 and 13.
Response: Thank you very much for your comments. We have named the key parts of the motor and made corresponding modifications, as shown in Figure 1 and Figure 13
Comment 3: Please describe the measuring elements of the test stand.
Response: Thank you very much for your comments. In our experiment, temperature sensors are mainly used, which are embedded in the motor during the assembly process. For details, We marked it in Figure 13.
Comment 4:How was the air friction loss determined (Figure 8). Please provide formula.
Response: Thank you very much for your opinion. The air friction loss is calculated by combining simulation and formula, and I have modified the corresponding part. (Please see section “2.3.3. Calculation of Cooling Conditions for Flow Field”, second paragraph.,Formula 9.)
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The reviewers criticism has been successfully addressed. I therefore recommend publication of the paper in its current form.
