High-Performance Five-Phase Axial Flux Permanent Magnet Generator for Small-Scale Vertical Axis Wind Turbine

Round 1

Reviewer 1 Report

A general remark concerns the choice to optimize the machine by minimizing the THD: a more complete explanation and discussion of this choice should be given, considering the following aspects:

• the machine voltages are the input of a diode rectifier, that is a source of additional waveform distortion; so, which is the need to improve voltage waveform quality, considering that the generator terminals do not feed any load directly?
• some parameter changes, in particular air-gap width and offset angle, can negatively affect other important performance figures of merit (for example winding factor, efficiency): this should be carefully taken into account, besides THD.

Please, add a discussion about these aspects.

In the following, all the other specific remarks and suggestions:

• title: "Vetical-Axist" should be corrected in "Vertical-Axis";
• line 13: "becomes" instead of "become";
• line 14: "country" instead of "county";
• lines 39-41: standard winding is a three one; so, multiphase windings should be windings with number of phases 4 or higher;
• line 52: the meaning of "capacity of a capacitor" is obscure: here it is introduced without any explanation; only at the end of the paper it is clear that it is referred to a filtering capacitor at the diode bridge rectifier output;
• lines 77,78: maybe the sentence "Result and discussion are discussed in section 3 and closed with the conclusion in section 4" could be changed in "Results and discussion are reported in section 3 and completed with the conclusion in section 4";
• lines 88, 89: the sentence "The winding type is changed from core wound to tooth wound to maximize the utilization of the stator winding" should be explained;
• line 90: "modified" instead of "repaired";
• lines 106-110: the different parts of the machine are indicated with letters a, b,..., k; the names a, b, c, d, e given to the five phases are not necessary and their introduction is confusing with the parts letters;
• line 114: row 1 of table 1: "233 and 135" should be written as "135 and 233" (inner and outer diameters);
• line 119: "wounded" should be substituted by "wound" (wounded means injured);
• line 124: "phosor" should be corrected in "phasor";
• lines 131-133: the sentence "From the figure ... 4b" is not clear and should be re-written;
• figure 4b: the yellow coils are scarcely visible and should be redrawn in another color (for example: green);
• line 151,152: "in start connection" should be corrected in "in star connection";
• line 175: a sentence should be added to explain how the disposition of fig. 6 is corresponding to that shown in fig. 2: fig. 6 topology is simply consisting of two axially coupled subsystems as in fig. 6? Please, explain explicitly;
• again fig. 6: the dimension B is not clearly visible: please, displace it;
• line 198: "non-linier" should be changed in "non-linear";
• line 207: it is written three neurons, but the hidden layer 2 of fig. 7 seems consisting of just two neurons;
• lines 220-260: the paragraph is very long and it contains comments concerning several following diagrams: it could be better to insert diagrams among the comment, to make more clear the understanding;
• line 252: "combination" should be "combinations";
• fig. 10: green and red diagrams consist of just two point: is it meaningful to consider a regression with correlation equal to 1 in these cases?
• line 286: table 6: the singularity of row 8 (predicted error = 32.87%) should be more completely discussed;
• lines 295-298: the sentence is not clear and should be re-phrased;
• lines 300-318: use dotted list and insert figures among comments, to make more clear the understanding;
• line 314: even if the Maxwell numerical format gives  3765.1912 Watt, it would be better to reduce the number of digits;
• line 316: which loss items are included in the reported efficiency value (92.45%)?
• fig. 12: the caption (a) reports "symmetrical position", but the two stator sides in the upper image appear displaced between them: please, check and/or explain;
• fig. 13, 14 and 15: the diagrams show that the adopted optimization reduces distortion and torque ripple; however, a significant reduction occurs also in the fundamental voltage component, in the average torque and in the output power: please, discuss in detail pros and cons of the adopted optimization criterion;
• line 341: the result 75.6135 volt should be reported with a lower number of digits;
  
• fig. 17: the table corresponding to the Maxwell calculated voltage waveforms reports an average value equal to 74.3884 V that differ with respect the previous declared value: why?

Author Response

Thank your very much for revising our manuscript

Author Response File: Author Response.pdf

Reviewer 2 Report

1. It is not clear that the power density is volume ratio [W/m^3] or mass ratio [W/kg]. The authors must mention the numerical power density.
2. The axial-flux machine presented in reference 1 is different in size. The authors must show the power density of the referenced machine and describe superiority of proposed machine.
3. It is good results that the ripple of moving torque is significantly reduced. But the authors don’t mention the spatial harmonics. We want to know the cogging torque of the proposed machine.
4. The structure of propose machine is very complicate. The authors must mention the mechanical realization of the proposed machine.
5. Does the title “Vetical-Axist Wind Turbine” mean “Vertica-Axis Wind Turbine” ?

Author Response

Thanks you very much for revising our manuscript

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The manuscript has been fully revised and significantly improved.

No further remarks or requests