Electrical Engineering

Electrical Engineering

  • Alexandros Kapsalis added an answer:
    Is it possible to tell comsol: only store specific parameters (like S11 in rf model)?

    i have performed a parametric sweep to evaluate S11 parameter with changing the width of my device, the simulation needs lots of memory and usually ends in error: out of memory! is it possible to tell comsol: only store specific parameters (like S11 in rf model)? and don't store the other parameter like the quantity of electric and magnetic fields in all nods and meshes in space?? because sometimes my simulation starts without error bur after some iteration the amount of needed memory increases and my PC can not provide the needed amount.

    Alexandros Kapsalis · National and Kapodistrian University of Athens

    Have you tried using probes only?

  • Axel Berres added an answer:
    What is the purpose of using 1.2 here in sine pwm in this simulink. In space vector pwm also I saw source voltage divided by 1.8. Why is it used?

    Please explain with sufficient theory

    Axel Berres · German Aerospace Center (DLR)

    First as i opened the model, the power lib is needed. If you want that we are capabale to analyse the model please wrtite the used matlab version and required libraries.

    Second. The model i opend was a 3 phase pwm rectifier and does what it has to do, rectifies input signals. Scaling the input signal (sin) means only to set the amplitude to a specific value not more. Setting the amplitude simulates the "real" input signal amplitude.

    I hope the answer helped.

    Kind Regards,

    Axel

  • Bekka Nassim added an answer:
    How is sizing of electric motors done for a motor running at variable load to achieve maximum efficiency?

    Motors frequently need to be operated under varying load conditions due to process requirements. Mostly a motor is selected based on the highest anticipated load. But the highest load can occur only for a short period of time. Instead a motor can be selected with a rating slightly lower than the peak anticipated load which can operate at overload for a short period of time. Example: For a particular load cycle, the average load is around 69kW with peak load(180kW) occurring for a few seconds. For this load cycle, it won't be cost efficient if we select a motor with rated power around 180kW. What is the appropriate way to select a proper sized motor that would operate at its highest efficiency for maximum time?

    Bekka Nassim · University of Nantes

    You can choose the RMS value of torque and speed during the cycle

  • E. A. Ogujor added an answer:
    What will be the change in the Line Data parameters in the IEEE standard Bus system if any line is considered as outage?

    What will be the change in the Line Data parameters in the IEEE standard Bus system if any line is considered as outage?

    E. A. Ogujor · University of Benin

    There will be a change in the bus impedance and admittances to which the line was connected and hence change in the power flow

  • Sofia D. Wechsler added an answer:
    How can I calculate the amount of needed voltage for electrostatically suspending a mass?

    Hi dears

    I'm going to design an electrostatically suspended mass system and I need to know the kinetics for calculating the amount of voltage that needs to apply on electrodes on top and below of the mass to create an electric field and suspending the mass.

    please help me as soon as possible 

    Sofia D. Wechsler · Technion - Israel Institute of Technology

    Albert Manfredi's post is the answer to the question.

    I would only add that if the mass is not point-like, if it has a volume, then there is also an Archimedian force which pushes the mass upwards. This force is equal in absolute value to the weight of the displaced amount of air. 

  • Mahdi Salimi added an answer:
    How can I increase the gain of a DC-DC Converter?

    I have designed a Boost Converter, now I want to increase the converter gain without changing the converter parameters. Is it possible any way?

    Mahdi Salimi · Islamic Azad University

    if you increase the converter duty cycle, voltage gain of the converter will be increased.

    if you have designed the parameters, you must improve elements structure and design.

    for example, if equivalent series resistances of the inductor and capacitor is reduced, the maximum accessible gain will be increased.

    Also, you can employ low voltage switches and diodes.

    however, in the standard boost dc-dc converter, maximum voltage gain is limited to 4-5.

    if more voltage gain is required, you can use other dc-dc boost topologies like Switched Inductor DC-DC boost converter.

    good luck

  • Roberto Andolfato asked a question:
    When is the vertical vector potential due to horizontal electric dipole negligible?

    Dear Colleagues, speaking about electric dipoles, we know VED produce only vertical vector potential while HED produce both horizontal and vertical vector potentials.

    My question is related to the HED vertical vector potentials.

    In my calculations, it seems that HED vertical vector potential is often negligible.

    I know solenoidal HED does not produce vertical vector potentials and probably at low frequency aerial or insulated souces can be considered solenoidal.

    Non insulated buried sources are not solenoidal but, if I consider an horizontal conductor divided in short elements, it seem that vertical vector potentials effects of each element are quite deleted from the adjacent elements and only the ends elements produce vertical vector potentials.

    I very appreciate your suggestions.

    Best regards Roberto Andolfato

  • Negin Kananizadeh added an answer:
    What is the Comsol Error Unknown function or operator; Name: intop1 - Feature: Time-Dependent Solver 1 (sol3/t1)?

    Hi,

    I'm defining a voltage in Component 1 > Definitions > Integration as

    Vip = intop1((comp1.mf.Ex*ix+comp1.mf.Ey*iy+comp1.mf.Ez*iz)*Np/area)

    I also tried defining Vip in global variables as

    intop1((comp1.mf.Ex*ix+comp1.mf.Ey*iy+comp1.mf.Ez*iz)*Np/area)

    But I get the errors:

    Unknown function or operator.
    - Name: intop1
    - Feature: Time-Dependent Solver 1 (sol3/t1)

    And:

    Internal geometry error.
    Error in multiphysics compilation.

    I have attached the file,

    Thanks a lot

    Negin Kananizadeh · University of Nebraska at Lincoln

    Hi Robert, I am glad that you have figured it out. 

  • John Fleming added an answer:
    What are your thoughts on renewable ocean energy, such as wave, wind and tidal energy?
    For example, Marine Renewables off the coast of Ireland has the potential to produce over 70GW of energy, more than 14 times the country’s current energy demand. There are many such examples speaking about the viability of ocean energy. A floating windfarm off Coos Bay in Oregon was approved! Are there such attempts in your country, maybe realized projects?
    John Fleming · University of Strathclyde

    Large scale development of tidal race power on the north coast of Scotland makes very good sense, particularly given the existence nearby to the south in the Great Glen of convenient sites for large scale pumped storage. The entire industry is in private profit-seeking hands and will respond to financial inducements. Legally (at present) these can only be offered by the UK government, not the Scottish government. Work is moving in this direction, but slowly.

  • Ruma Debnath added an answer:
    In a spectrum Full width with half maximum of all wavelength, will peaks be the same or different?

    Spectrum Range=1300nm-1360nm. 

    Ruma Debnath · National Institute of Technology, Agartala

    Thank you all.

  • Jitendra Nath Rai added an answer:
    How can I solve five non linear equation roots with five equations with newton raphson method?

    cos(x1)+cos(x2)+cos(x3)+cos(x4)+cos(x5)=0.9;;
    cos(5(x1))+cos(5(x2))+cos(5(x3))+cos(5(x4))+cos(5(x5))=0;;
    cos(7(x1)))+cos(7(x2))+cos(7(x3))+cos(7(x4))+cos(7(x5))=0;;
    cos(11(x1))+cos(11(x2))+cos(11(x3))+cos(11(x4))+cos(11(x5))=0;;
    cos(13(x1))+cos(13(x2))+cos(13(x3))+cos(13(x4))+cos(13(x5))=0;;
    0<x1<x2<x3<x4<x5<90degree;;
    where x1,x2,x3,x4,x5 are angles in degree..

    How to solve it with Newton-Raphson ? How to write these functions in matlab coding?

    Jitendra Nath Rai · Delhi Technological University

    You can use the least-square method as suggested byGraham W Pulford.

  • Srikanth Reddy added an answer:
    How can wind-pumped storage coordination increase dispatchability in a day ahead programming,whereas the wind curtailment is not definite yet?

    How can wind-pumped storage coordination increase dispatchability in a day ahead programming,whereas the wind curtailment is not definite yet one day before real time?

    In other word, available wind power is not definite when ISO will determine commitment of day ahead program. on the other hand, wind curtailment is the difference between available and forecasted wind power.

    Srikanth Reddy · Indian Institute of Technology Delhi

    Curtailment is more often defined as a state of wind generators not being able to transmit/dispatch the wind generation due to limitations of transmission network or the load is being already met by the committed generation other than wind. But, the context of pumped hydro storage is more related to managing variation in predicted and actual generation (higher or lower). Therefore, curtailment is more of an issue related to infrastructure/transmission/connectivity of network. Whereas, storage is related to capitalization of wind energy in case of higher actual generation and improvement in dispatchability in case of lower actual generation than the predictability. In case of transmission congestion, dispatchability becomes the job of transmission system operator who takes over the day ahead market operator to alleviate the congestion through real time locational marginal prices. 

  • Alex Van den Bossche added an answer:
    How does the operating frequency influence the leakage inductance between two coils?

    We know that leakage inductance depends on the distance between the two coils and coil/size ratio. If we consider two loosely coupled coils, what does the frequency vs leakage inductance curve look like?

    Alex Van den Bossche · Ghent University

    For low frequencies, the current is homogeneous in a conductor. The inductance contribution in the conductor itself is it is mu*1/(4*pi)*length. In conductors far away from other conductors this contribution vanishes at high  frequency. This is an example of transmission lines at low frequency, one observes an inductance in coaxial wires even if inner touches outer.:

    http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/busbar-and-primary-circuit/

    One observes an inductance even if wires touch. If conductors are close, the eddy currents tend to let the current flow on the surface side close to the other conductor, so on sides and concentrated, so the leakage gets the difference low-high frequency is more than mu*1/(4*pi)*length. In a coil, wires screen somewhat the field and the inductance is reduced.

    Bessel type equations give the impedance for a stand alone wire. The imaginary part contains the inductive part. In a conductor in transverse field, one can get also other Bessel equations. I deal with this in chapter 5 of the book "Inductors and transformers for power electronics", but I did not emphasize on inductance change as it has a minor effect on losses.

    Impedance functions are analytic functions, so real and imaginary part are linked. So if one knows the change of the resistive part of the impedance, one could predict the inductance change.

    Accurate finite elements can model it, but one needs a fine mesh at the conductor surface to model well the eddy currents. If there are many wires and strands finite elements get problems.

  • Sounik Kiran added an answer:
    What is the difference between Returnloss(dB) and S11(dB) ?

    Actually some research papers have written Returnloss(dB) and some others have written S11(dB). Couple months back I had seen there was an article in IEEE which has given the clarification. If any one have any information kindly tell me.

    Sounik Kiran · National Institute of Technology, Silchar

    Thank You Xavier Le Polozec, Abdelhalim Zekry, Sandra Cruz-Pol  for your suggestive answers.

  • Mahamad Nabab Alam added an answer:
    What are the most recent advances in design of poles for electricity distribution?

    We are working with a company which manufactures utility poles and we are looking for some ideas to develop new products for this company. Some topics could be the following:

    - New designs for preventing electric shocks or accidents

    - New designs or materials to reduce the effects of corrosion in shore areas

    - New materials to make the poles cheaper and stronger

    Mahamad Nabab Alam · Indian Institute of Technology Roorkee

    You may get some additional information in the book available here:

    http://accessengineeringlibrary.com/browse/handbook-of-electrical-design-details-second-edition

  • Mohammad Habib Ullah added an answer:
    Any suggestions about Cross-Correlation computation and it's maximization?

    1) Let us say, I have  2x2 matrices A and B. I have another matrix C which is 4x4 , that is , C=[A X ; XT B]. Where X is the 2x2 covariance matrix between A and B. How can I calculate Correlation Coefficient?

    The formula of Correlation Coefficient for two random variables X and Y is Corr=Cov(X,Y)/Std(X)*Std(Y). How can I calculate Correlation coefficient in above case?

    2) If I have a Matrix A=[2 0;0 9]; If I rotate this matrix between 0 to 360, I get a maximum correlation of -0.6365 to 0.6365. How can I achieve maximum correlation of 1 or 0.9 for this matrix using rotation?

    Kindly help me out. Any suggestions and comments?

    Mohammad Habib Ullah · University of Malaya

    If it is in Matlab than you can use

    The sample given is done based on LScode2

    code=LScode2(11);

     for i=0:7

        for j=-8189:8190

      cc(i+1,j+8190)=sum(code(1,:).*circshift(code(i+1,:)',j)');

        end

    end

    close all;

    subplot(111);

    for i=1:8

        subplot(4,2,1);

        stem(cc(i,:),'.');

        title(['Cross correlation of code ',num2str(1),'and code ',num2str( i)]);

    end

  • Jeydson Lopes added an answer:
    How to simulate a BELBiC controller in matlab for transformer protection?
    How to simulate BELBiC controller in matlab for transformer protection?
    Jeydson Lopes · Federal University of Pernambuco

    Sir
    My e-mail id is jeydsonL@Gmail.com  /     jeydson_new@hotmail.com
    Please send me an BELBIC simulink model to this e-mail.

    I really thank

  • Shahid Hassim added an answer:
    Which company makes "wind turbine emulator for laboratory purpose" ?

    I want to purchase "wind turbine emulator for laboratory purpose", Please suggest some manufacturing companies for wind turbine emulator.

    I know only two companies "Ecosense and Festo Didactic", please suggest some other.... 

    Shahid Hassim · National University of Ireland, Galway

    You may want to have a look at this : https://www.labvolt.com/solutions/6_electricity_and_new_energy/98-46120-00_solar_wind_energy_training_systems

  • Partha Sikder added an answer:
    Can someone give me some advice relating to the Shunt Active Power filter?

     I have design the system in Matlab simulink, but when i start the current injection in the grid, my Source current become doubled also load current become less. I dont know this is active filtering or not.

    Second, I am confuse about the PCC, when we inject current why the amplitude of the Source current changes,

    Third, Can i keep the Vdc voltage of the capacitor initial voltage constant before start the simulation.

    Partha Sikder · Jadavpur University

    Can u please send me the paper???

  • Ashish Chittora added an answer:
    What is actually reactive power?

    From the basic engineering itself this question has posed me lot of trouble. The main reason is that there is lot of explanation available and few contradict each other. For example, one explanation was it is the medium through active power is transferred, if that is the case then what about DC power transfer? 

    So here i would like to know your opinion on the concept of reactive power and would like to discuss each and every view so that i can have a clear cut understanding of 'real REACTIVE POWER'. 

    Ashish Chittora · Indian Institute of Technology Bombay

    Reactive power is actually the stored power in the circuit, which is not getting transferred to the load, nor it will be lost as heat. It is due to inductance/capacitance present in the circuit. 

  • Alexander E Kaplan added an answer:
    Is it possible to have light without electrical power?

    In general, light is produced for household purpose with bulb, CFL, tube, LED etc from electrical power. There is a big portion of world that lives in dark after sun sets. These people do not want electrical power, they want light first.


    Is it possible to create a pollution free light without electric power and without burning something. Light that is sufficient to illuminate a 12 x 12 feet hut without an electricity connection. Light that is very very cheap (not more than $1 per week and 8 hours per day)….Don’t tell solar or known things….suggest something wild…some new idea….innovative…no power only light….Just for the sake of discussion….

    Alexander E Kaplan · Johns Hopkins University

    @Vasile: Nah... it was simply because If you think big enough, you'll never have to do it..:-)

    As to a fake universe, well, here is another/better thought: Reality is merely an illusion, albeit a very persistent one. ( Albert Einstein )

    For many other great philosophical ideas, see

    http://psi.ece.jhu.edu/~kaplan/off-the-wall.html

  • Samba Sowe added an answer:
    Does anyone know where I can find a DIgSILENT PowerFactory tutorial?
    Does anyone know where I can find a DIgSILENT PowerFactory tutorial?
    Samba Sowe · Naresuan University

    http://fglongatt.org/OLD/Tutorial_DigSilent_EN.html

    This website provides a set of my experiences on use of PowerFactory. I tried to put together in pedagogical way. The objective is give a useful information about the PowerFactory use and increase penetration of this software at all level. The documents here are free to be used in all ways. Just keep the copyright.

  • Mehdi Ouada added an answer:
    Sometimes we use an integral action to avoid static errors. What does it means?

    Sometimes we use an integral action to avoid static errors. What does it means? A+.

    Mehdi Ouada · Badji Mokhtar - Annaba University

    in my opinion for more accuracy

  • Biplab Nayak added an answer:
    In the construction of a transformer why circular(cross-section) core is not used?

    in construction of a transformer cruciform core has more advantage than a square shaped .if we use a circular core it will be much more advantageous.

    Biplab Nayak · Bhubaneswar Institute of Technology

    - Cruciform core reduces the diameter of circumcircle. Due to less diameter of circumcircle, the insulating material required is less. 

    -Length per one turn is less so that amout of copper required for winding can be reduced.

    -Due to above reasons size, weight and cost of transformer is less with cruciform core.

    -Cruciform core has more utilization factor.

  • Upendra Reddy added an answer:
    Any advice regarding synchronous speed estimation in voltage model Direct Torque Control?

    i am implementing  Classical DTC in simulink with improved stator flux estimation [Algorithm which was proposed in paper AN IMPROVED STATOR FLUX ESTIMATION IN STEADY STATE OPERATION FOR DIRECT TORQUE CONTROL OF INDUCTION MACHINES  ],during this implementation i am facing problem to estimate the synchronous frequency.

    As it was given in paper that

    We ={ [ V - i*r] / (Si_s^2 )} .  j si_s

    my doubt is that as the voltage is pulsed stepped waveform of magnitude 2/3*Vdc peak  to  peak and subtraction of i*Rs drop gives the result of emf(v-i*rs) of (2/3*Vdc) +/- 20 , and the wave form look like voltage wave form.How can we get synchronous frequency from this noisy waveform even after it has been divided with si_s^2 and it multipled with j*si_s.

    Kindly reply

    Upendra Reddy · Indian Institute of Technology Guwahati

    Thank you

  • Mohamad Hoseiny added an answer:
    What is the best software for simulation of Power electronic projects?

    Hi

    What is the best software for simulation of  Power electronic projects such as DC/DC converters with high Input-Output Voltage or Current? I think that MATLAB(Simulink) some times is not good for them.

    Best Regards.

    Mohamad Hoseiny · Khorasan Institute of Higher Education

    hi

    in the matlab

  • Parul Nilesh Shah added an answer:
    What are the good open source alternatives to MATLAB?
    I am trying to find an open source software package that should be as good as MATLAB.
    Parul Nilesh Shah · Vubites India Pvt. Ltd.

    I have been using OCTAVE now for almost two years and am happy with it. My work is in image and signal processing. It doesn't provide GUI but then who needs it for research work. Besides, its video processing toolbox is still not in place so if you are into video processing you might want to look for some other options. Do let us know what you finally found useful.

    Good luck...

    Parul

  • Adeola A. Adedeji added an answer:
    Which indexing service does present better evaluation? ISI or Scopus?
    Or other indexing service?
    Adeola A. Adedeji · University of Ilorin

    ISI and Scopus are in a group and do not involve all publications but insist on Journal recognition, but Google Scholar is unique.

  • Pascal Venet added an answer:
    How does the lifespan time of the supercapacitors depend on current and cycle profile?

    In datasheet of the supercapacitor is given Projected Cycle Life at 25°C
    by Test Current 100 A. But if supercapacitor is used at higher rated current, how to decrease the number of cycles. Or if supercapacitor is used at rated current 100 A but current profile is different as in datasheet. Is there any relationship between life time and cycle profile?

    Pascal Venet · Claude Bernard University Lyon 1

    Dear Dimitri,

    Yes you can use this empirical law as you indicate.

    See my answer to your mp for details

    Best regards

  • Khaled Rady added an answer:
    Does anyone know what are the advances in the modern gas centrifuge tech. that didn't exist in the old zippe type?

    I am currently working on modelling of gas centrifugation process and the effect of implementing "MAGLEV and advanced control tech." to reduce the gas centrifugation power consumption. However,  the only model that I could find online was the original zippe type centrifuge which has a very low SWU. Hence, it can never achieve the isotope SWU mentioned in the DOE or NRC.

    So, I wonder if anyone can appoint me to some researchs/researchers to get any info. about the current types of the gas centrifuge (physical model, mathematical model, manufacturers ...etc)?

    Khaled Rady · Cairo University

    Dear Dr.Anthony

    I deduce from your comment that the proliferation issues is not limited to the systems prototypes only but it is also applied to the system simulations using softwares as well. I have already found the data I needed for the system published by the DOE on the Internet. However,  I really appreciate your consideration.

    Best regards, 

    P.S. the attached fig Source is: Khan Research Laboratories; David Albright, Institute for Science and International Security

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