Electrical Engineering

Electrical Engineering

  • Gergo Vassilev added an answer:
    Sheet resistance measurement with multimeter?
    Does anyone know how to measure sheet resistance of a material (polymer solution) using potentiostat?

    If resistance is high, than probaby you will have to use sandwich set up (electrode- polymer-electrode).

    If resistance is low and substrate is rectangular, than you can use electrodes on top of the polimer. Prefered is to cover the whole oposite edges with the electrodes.(for example- 1/8 of the surface as electrode, 6/8 as m If you cover partially the oposite edges, then the extra material, that is not between the electrodes will also influence.

  • Bharti Dwivedi added an answer:
    Can anyone explain in detail three terminal protection?

    Can anyone explain in detail about three terminal protection using gas discharge tube, transient voltage suppressor, and fusible resistor for data line protection?

    Bharti Dwivedi · Institute of Engineering & Technology - Lucknow

    The device / equipment / system to be protected should be revealed in the question.

         
  • Sujit K. Biswas added an answer:
    What are the advantages of free wheeling diodes in full wave rectifiers?

    Thanks.

    Sujit K. Biswas · Jadavpur University

    The question asked for the advantage of a free wheel diode at the output of a full wave rectifier, but why are so many people talking about using antiparallel diodes across semiconductor switches or reduction of arcing? It is not the same.

  • Vyacheslav Lyashenko added an answer:
    Why people answer my question with a search from google?

    Why people answer my question with a search from google?

    Vyacheslav Lyashenko · Kharkiv National University of Radio Electronics

    Dear Mostafa. It's very simple. RG - this communication, and play. Questions and answers - this rating. Hence the desire boost their ratings.
    This also applies to the question: Why people answer your question with a quotation from wikipedia ?.

  • Arijit Basuray added an answer:
    How many types of cooling system are there for transformers?

    Thanks.

    Arijit Basuray · Jadavpur University

    All the above replies are relevant and appropriate and described the conventional and popular methods of cooling transformers. The essential requirement of cooling is designing a proper heat pipe so that heat can be taken out from the object under consideration so you may expand your imagination to cool a transformer particularly if it be a non standard transformer. As an example in a Transformer with very high current capacity and lower voltage rating the secondary winding can be in the form of a pipe and cold water flowing continuously through it for cooling the winding. Since Dry type transformers as rightly pointed out by Mr. El-Fergany can be cooled by natural or forced air only some time you may try with  typically designed heat sink with or without  forced air for more effective cooling particularly for low voltage system.

  • H.J.L. Witte added an answer:
    Is there any in-depth consistency between energy and information?

    It is a hot topic in the electrical engineering area called "the energy internet", which aims to incorporate different types of energies together, while managing and utilizing the energy in a macroscopic point of view.

    However, is there any in-depth consistency between energy and information? If it is true, then some of the concepts, methodologies etc of the "information network" can be used to deal with the "energy internet", while a lot of issues in current power network can be explained in a totally different way.

    H.J.L. Witte · Groenholland

    Dear Zhigang,

    With regard to electricity networks one thing you should IMO not overlook, and which is a difference with information, is that the network itself stores energy (in magnetic fields etc) and therefore the response and requirements to switching will be quite different.

    To formally define networks my guess would be that graph theory would be a good basic methodology to define switching networks and routes.

    Regards,

    Henk Witte

  • Kittipong Tripetch added an answer:
    Does anybody know where I can get the schematic of the ideal opamp in cadence ahdlLib?

    I need the internal circuit design to compare it with my design. I am not getting the same results. I cannot make my opamp go to unity gain.

    Kittipong Tripetch · Keio University

    Ideal op amp is just black box , you should used spice instead, usually, Manufacturers have some spice macro model of it. It depends on the specification of that part number of that brand. Some op-amp part number have no library you should model macro model by buy that opamp and do some experiment to extract pole and zero frequency from power spectrum. By  extract input and output impedance parameter from scattering parameter which you can measured with spectrum analyzer or network analyzer 

  • Praveen Kesavan added an answer:
    What are the possible failures of a BLDC servomotor operating under high ambient temperature conditions?

    Whether hall sensors integrated within the motor also contribute to the failure?

    High temperature ambient conditions approximately refers to 423 K .

    Praveen Kesavan · Indira Gandhi Centre for Atomic Research

    The insulation and magnets may be available which can cope up with 150oC, but during the operation the temperature still rises. Whether hall sensors can withstand high temperature when it is integrated inside the motor?

  • Mostafa Eidiani added an answer:
    What is difference between AC Optimization (Interior Point Method) and DC Optimization (Linear Programming)?

    What is difference between AC Optimization (Interior Point Method) and DC Optimization (Linear Programming)?

    Mostafa Eidiani · Khorasan Institute of Higher Education

    I find these links:

    http://en.wikipedia.org/wiki/Interior_point_method

    http://www.princeton.edu/~rvdb/542/lectures/lec14.pdf

  • Mostafa Eidiani added an answer:
    Why single phase short circuit current near to generators is greater than three phase short circuit current?

    Why single phase short circuit current near to generators is greater than three phase short circuit current?

    Mostafa Eidiani · Khorasan Institute of Higher Education

    Hi

    I find this file

    http://www.dii.unipd.it/~gobbo/didattica/corsi/Componenti_tecnologie_elettrici/ABB_swithgear_manual_E11/ABB_11_E_03_druck.pdf

  • Mostafa Eidiani added an answer:
    What does "voltage steps" mean in contingency ranking?

    What does "voltage steps" mean in contingency ranking?

    Mostafa Eidiani · Khorasan Institute of Higher Education

    I find these links:

    http://www2.ing.puc.cl/power/paperspdf/dixon/32.pdf

    http://www.ijims.com/process/downloadPDF.php?id=132

    help Digsilent

    All voltage deviations of terminals (between the base case and the contingency case) for each contingency are displayed in a single list. Reports the highest voltage deviation of terminals (between the base case and the contingency case) considering all contingencies. Any such terminal is reported only once. Only terminals with the highest voltage deviation greater than the specified maximum voltage step are reported.

  • Jan Sikora added an answer:
    What does "consider voltage dependency of loads" mean?

    What does "consider voltage dependency of loads" mean?
    Loads are voltage dependent or Voltages are load dependent?

    Jan Sikora · Lublin University of Technology

    Hi!

    Loads are voltage dependent  - IT MEANS THAT WE HAVE TO CONSIDER A NONLINEAR LOAD

    or Voltages are load dependent?

    IN THE SECOND CASE WE HAVE THE CURRENT SOURCE OR THE VOLTAGE SOURCE IS NOT IDEAL (ITS POWER IS LIMITED).

  • Shashwata Rahman added an answer:
    Does a single stage op-amp is enough for generating a voltage just to match the circuit to a 50 ohm load?

    I don't require it to amplify anything I just need it to basically work as a feedback amplifier to get the voltages at the inverting and noninverting same by generating a matching voltage. I used a default amp for the design, but my supervisor said that I have to design my own amp. Here is the image of a circuit similar to what I have designed. I know it's a silly question, but just wanted to check if A single stage op amp is fine for the application.

    http://snag.gy/UDHjD.jpg

    Shashwata Rahman · RWTH Aachen University

    Any body knows how I can get the schematic or make an opamp functioning exactly like the opamp in ahdl lib in cadence. The thing is I made my devices based on that but now the opamp I designed is giving a slightly varied results. I have to make a opamp myself as the institute doesn't allow to use opamps provided by cadence. Probably this question is insanely stupid but I really dont have so much time to work on an opamp as I have other devices to work on. Thankyou in advanced.

  • Samir Ben Abid added an answer:
    Can I use IC MC 1648 for VCO based chirp generation?

    Hello.

    I'm Nur Aeni from Indonesia. I want to ask you about VCO based chirp generation. I have built a chirp generator from VCO. I used IC MC1648 for VCO, but I have a problem, when I input ramp signal from Xr2206 module to VCO, the chirp signal does not come out. My question is, can I use IC MC 1648 for VCO?

    Thank you in advance

    Perhaps you should opt for a DDS (like AD9850 for example http://www.analog.com/static/imported-files/data_sheets/AD9850.pdf) . You can find developement boards, with all the analog parts pre-installed, for less than $10.

    A simple microcontroller driving the DDS should be enough to generate the needed signal. You can even bitbang the SPI signals using an FTDI chip and control the chirp generator from Simulink, for example.

  • Daniel Oladapo Olaniregun added an answer:
    How is it possible to put torque on the shaft of a two co-axial coupled similar induction motors which are in opposite of each other?

    .

    Daniel Oladapo Olaniregun · DEUS GLOBAL NIG LTD

    Get a differential gear system. Just exactly what you have at the back of you axle driven car or truck. Fix the two rigid support on a rigid frame. Couple the two motors on a coupler with steel pulley or friction drive solid tire like you have on a tricycle. Make your three phase connection of the two motor to run in the same direction( Synchronization)

    Use Anti-slip belt to tap the power on the pulley and antivbration Damper coupler

  • Hany Ferdinando added an answer:
    How can I put cluster labels in the Gaussian Mixture Model (GMM)?

    I used GMM to cluster my data. It has 4 dimensions with 3 clusters. The GMM ran very well, and I got the mean and covariance matrix for each cluster.

    The problem is I don't know which label belongs to which cluster. In addition, the cluster labels changed whenever I ran the iteration.

    For example, in the first iteration, the cluster labels were 1, 2 and 3. In the second iteration, the cluster labels were 2,1 and 3, etc.

    Can I fix the cluster labels? If yes, how do I do it?

    Hany Ferdinando · University of Oulu

    Thank you, Farid! I will try it

  • David McLennan added an answer:
    What is the effect of the tap changer on HV or LV side of the transformer?

    What is the effect of the tap changer on HV or LV side of the transformer?

    I think this practice varies between countries. I understand that HV tap changers are usual in Europe and LV tap changers are common in America. The LV tap changers break larger currents so contact maintenance and oil condition can be a maintenance issue. 

  • Robert Schwerdfeger added an answer:
    In quadratic cost function of power generation units, what are the costs that vary as the square of power generated?

    In a, b and c constants, b stands for those costs which are proportional to the power generated say like fuel cost, c stands for the costs to be met even when there is no power generation, say like interest on borrowed capital etc. Like wise what costs does a stand for?

    Robert Schwerdfeger · Technische Universität Ilmenau

    You are welcome.

  • Shahrukh Shamim added an answer:
    The best way to extract papers from project?

    What is the best method to extract papers from academic projects?

    Shahrukh Shamim · Maulana Azad National Institute of Technology, Bhopal

    I think that it depends on how useful findings are there in the academic project which can be industrially applicable or can be useful in any other aspects. If it is successful in giving a clear understanding of the topic discussed with proper results and conclusion of the problem, then you can share your findings through a Research Paper. 

  • Robert Schwerdfeger added an answer:
    What do "unsupplied area" and "isolated area" mean in power system?

    What do "unsupplied area" and "isolated area" mean in power system?

    Robert Schwerdfeger · Technische Universität Ilmenau

    In my opinion they are both kinds of islanded grids. Thereby an unsupplied area means that the grid area is not electrified for example caused be islanding or generatio unit switch off or both. On the other hand isolated areas are independent working (micro-)grids, which are electrified by connected generation units. For example in China there are some regions which are still not merged to the "main" grid.

  • A. Khattara added an answer:
    How can I get a MATLAB code for unbalanced system power flow analysis?

    Since I am working on unbalanced power flow analysis using backward/forward sweep methods, I need MATLAB code.

    A. Khattara · Université de Biskra

    try to use a grid softwer as PSAT or CYME

  • Sebastian Michael Strauch added an answer:
    Why people answer your question with a quotation from wikipedia?

    Why people answer your question with a quotation from wikipedia?

    Sebastian Michael Strauch · Friedrich-Alexander Universität Erlangen-Nürnberg

    Because if you google anything, wikipedia will show up pretty high up in the hit list.

    Besides, wikipedia is a great source for information, and if you do not trust it (as a lot of people do, usually those who do not contribute) you might want to check the references at the bottom of each page. There you might find a source more "trustworthy" on the subject.

  • Mohammad Malek Mohammadi added an answer:
    How can I design and simulate a sliding mode controller for a nonlinear system such as PV systems (MPPT)?

    Hi

    How can I design and simulate a sliding mode controller for a nonlinear system such as PV systems (MPPT)?

    I am looking for useful articles about sliding-mode control systems.(Design and Simulation)

    Best regards.

    Mohammad Malek Mohammadi · Khorasan Institute of Higher Education

    Thanks for all.

  • Alex Van den Bossche added an answer:
    How can I detect islanding in a grid-connected converter?

    The study and development of anti-islanding controls are very important in wind and solar applications.

    Alex Van den Bossche · Ghent University

    In Germany there was a big problem that renewables were thrown of the grid at a big grid transient (Saling ship with open high voltage line at the Elbe). Those reguations should be abandonned as they have their origin in alternators. If you disconnect an alternator at light local load, the frequency rises and the voltage may rise also. But why should a frequency from a converter rise? So, this principle is not valid for converters. In converters, one will mainly see it in voltage not in frequency.

  • IRFAN AHMED HALEPOTO added an answer:
    As a broad area to start with can some one suggest recent problems to be addressed in designing class D amplifiers?

    Pulse Width modulation associated leads to issues like Electromagnetic Interference, Harmonic distortions and so on. As I work on Higher Peak Mean Power Output causing Device energy losses is also of concern. I prefer to work on Audio amplifiers.

    IRFAN AHMED HALEPOTO · Mehran University of Engineering and Technology

    Digital Switching Amplifiers (commonly known as Class-D) have been around for years. Nevertheless, it is nearly impossible to engineer a conventional Class-D amplifier that handles the full requirement, 20-20,000Hz, for full-bandwidth music reproduction. A Class-D amplifier works by utilizing a high-frequency sawtooth waveform to modulate the music signal (to learn more about how Class-D amplifier works, click here).


    The constant presence of the sawtooth waveform, which is very high in frequency spectrum and its inevitable frequency jittering, can mask or corrupt low-level music signal. The output filter designed to filter out noise and overtones caused by the sawtooth waveform adds a 180 degree phase shift to Class-D output stage, causing possible instability and adding distortion due to its own inherent non-linearities.

    Additionally, the output filter presents frequency-variant output impedance that can interact with a speaker's complex impedance. Variants of Class-D amplifiers with the addition of Digital Signal Processor claim to improve music reproductions. However, because of their lack of close-loop design, especially from the speaker's terminals, spurious interaction between the speaker's complex impedance and back-EMF with the amplifier's resonant output filter can result in harsh sound reproduction. The fundamental flaws of conventional Class-D amplifiers remain unresolved.

  • J.A. Heerdt added an answer:
    What are the basic limitations of a load compensator?

    Assuming the compensator is a power electronics based device (e.g. a STATCOM), what are its main limitations to achieve the ideal characteristics, e.g. error-less reference current tracking?

    Also, how are these limitations related to the applications that the compensators are utilized for? For example, are the limitations of pure reactive compensator different than those of non-sinusoidal current compensator?

    J.A. Heerdt · Universidade do Estado de Santa Catarina

    Hello Amin!

    To compensate non-sinusoidal currents you need more bandwith and to compensate pure reactive power you need more power. Both of them have the natural difficulty of tracking a sinusoidal shape reference.

  • Kudzai Gwanzura added an answer:
    What is the best way to dim an LED?

    If i wanted to dim a bank of LED bulbs/lights via a mobile phone, what would be the best method to do that and how do I implement it.

    Kudzai Gwanzura · University of KwaZulu-Natal

    Thank you very much Kid Cowles

  • Ankit Choudhary asked a question:
    How to perform 3D TCAD Sentaurus simulations for large devices say 100 nm channel length?

    This is taking too much time to simulate and I need to find a workaround.

  • B. Rajanarayan Prusty added an answer:
    What is the expression for load current in an RLC AC circuit?

    What will be the expression for output current in a RLC AC circuit through the load R when frequency of the supply is varied? If the resulting equation is nonlinear then justify how for a linear circuit the resulting equation is nonlinear?

    B. Rajanarayan Prusty · National Institute of Technology Karnataka

    Thank you all for your participation.

  • Rakesh Kumar Srivastava added an answer:
    How can I design calculations for a PCB Stator Winding in an Axial Flux BLDC Motor?

    Can you provide me some research papers or books on this topic?

    Rakesh Kumar Srivastava · Indian Institute of Technology (Banaras Hindu University) Varanasi

    Refer book by M.G.Say & E.O.Taylor Direct Current Machines, ELBS, London, 1980

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