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  1. n.karthick

    Field Oriented Control Clarification

    Hi, The controller is normally designed in such a way that it acts like a mirror image of the physical system it is going to control. In this case, the physical system i.e, the motor takes voltage as input and its response is measured as current. We know the mathematical model of the motor...
  2. n.karthick

    DC Drive rating to run DC Shunt Generator

    You may need to consider the losses in the motor (its efficiency) while calculating the required motor rating for your generator.
  3. n.karthick

    Simulink help for getting a frequency I can use as an input

    Hi, You can use PLL block in Simulink to find the frequency of the signal. Both single and three-phase PLLs are available in Simulink.
  4. n.karthick

    Three phase supply

    The phase means the angular difference between the sinusoidal voltage on one wire to another. For three phase, the angular difference would be 360/3 = 120 deg. Instead of having three independent single phase transmission system which require (phase + neutral wire for each phase) 2*3 = 6 wires...
  5. n.karthick

    Three phase circuits

    The arrow denotes the sign of voltage induced in the winding when current flows in that direction. For example if current flows from terminal n to R, the voltage across the winding denoted by VnR is positive.
  6. n.karthick

    Matlab: How to get the PSD of a signal?

    Which version of matlab you are using? i am using matlab 7.8 R2009a. In my version I have a function called 'dspdata.psd' in signal processing toolbox to find psd of input data.
  7. n.karthick

    How to get amplitude and phase

    There are many methods available. Short time Fourier transform, Wavelet transform, least squares method, auto regressive methods etc.
  8. n.karthick

    Understanding concept of Zener Diodes for voltage

    The Vout will be negative (as Vin is negative and you are using non-inverting amplifier). This Vout is clipped by Z2 to -5.7 V
  9. n.karthick

    Passive Sign Convention

    The fact is current never enters the negative terminal of a resistor (in the sense you mentioned) and the power will never be negative.
  10. n.karthick

    Passive Sign Convention

    This is wrong example. A resistor can only dissipate power and it can't never supply power.
  11. n.karthick

    A question on votage

    A will be more positive than B if current enters at A i.e, when Ir is positive The sign of Vr depends on direction of current flow which is depicted in the picture.
  12. n.karthick

    Help need Fo DC ANd AC

    Surely it should read zero, because average of sine wave is zero.
  13. n.karthick

    Need help in matlab simulink ?

    Hi, Double click the "Error rate calculation block. In "Output data" combo box select "Port" instead of "Workspace". Now you can connect Scope to it
  14. n.karthick

    (signal processing)Time domain vs Frequency domain, totally confused!

    No, Y(s)=1/s If you want y(t) you have to take inverse transformation of Y(s)
  15. n.karthick

    (signal processing)Time domain vs Frequency domain, totally confused!

    Though I dont know much I can tell what I know about frequency domain calculations 1) It is just a mathematical technique and has no physical implications. The signal whether represented in time or frequency domain has no change in itself and only the way it is viewed is different. So both are...
  16. n.karthick

    Yet more electrical attraction

    I feel for 1) the capacitance is decreased, but distance between the plates is increased, so it wont be a problem since same charges are far apart.
  17. n.karthick

    Need a two wire ac voltage rectifier

    Using half wave rectifier you will get 54 V dc for 120 V ac input. If you want till less you can use controlled rectifier using thyristors/triacs, which are very common nowadays. By controlling the firing angle the output voltage can be varied smoothly from 108V to 0 V. Brief introduction...
  18. n.karthick

    Basic Inductor Concept

    If we neglect the small resistance r of the winding then flux is 90 deg lagging wrt voltage. Otherwise as you said it is lagging by phase \phi only
  19. n.karthick

    Signal and system

    Fourier transform(FT) is the generalization of Fourier series. In FT you get frequency spectrum of a function f (if FT exists for f) and instead of spectrum you get discrete frequencies if f is periodic. Note: Both FT and fourier series are approximations of f
  20. n.karthick

    Voltage source connected with parallel.

    If no diodes are added and if the internal impedance of the sources are not equal then there will be circulating currents between the sources, even if their voltages are same,which is highly undesirable. That's why we should add blocking diodes.
  21. n.karthick

    Substation Capacitor Bank Problem

    Even though I am not sure, it could be due to resonance between your capacitor bank and a nonlinear load connected to the same point. Since nonlinear load draw harmonic currents, resonance may happen at higher frequencies resulting in huge current and fuses may blow up.
  22. n.karthick

    How to convert dc voltage into higher dc voltage using transformer?

    You can use boost converter to step up DC. Basic information can be found in wikipedia page http://en.wikipedia.org/wiki/Boost_converter
  23. n.karthick

    Efficiency calculation

    Because efficiency = output energy / input energy You know losses = 25%=0.25 therefore output energy you get is only 75% (100%-25%). efficiency = 0.75. So if you want to find input energy output energy has to be divided by 0.75.
  24. n.karthick

    Capacitor and their behavior in AC

    But SimPowersystems of Simulink/Matlab wont give you correct results. It too have R, C and DC sources. If you simulate a simple RC circuit with DC source in SimPowersytems, Capacitor is instantaneously charged, no matter how much value of R is kept. I think it is a bug in the software. I dont...
  25. n.karthick

    Meaning of Laplace Transform

    Hai you can refer to this book Circuits and filters handbook chapter 3 on Laplace transform. https://www.amazon.com/dp/0849383412/?tag=pfamazon01-20 I had the similar doubt like you. After reading the above book, I could understand how Laplace transform (LT) works. It is better if you...
  26. n.karthick

    Thevinin and Norton

    The basic difference is, for the given complex circuit with many elements, in Thevenin terms, we find equivalent voltage Vth and resistance Rth across a point AB ie., the circuit is simplified in to a voltage source in series with a resistance connected to AB. While in Norton terms, we find...
  27. n.karthick

    Doubt in semiconductor diode theory ?

    It is not like that. The current outside the diode terminals (i.e., in the wire) is due to flow of electrons only. But inside the diode, the holes actually did not move. It is the electron which move forward and leaves a hole in backward direction, so as the electron progresses, it appears that...
  28. n.karthick

    Regarding Backup UPS operation

    Thanks for your replies. Actually I am using this UPS for my computer in my home, which I use only in night time. I can't switch ON my UPS all the time, because it is unnecessary.
  29. n.karthick

    Regarding Backup UPS operation

    I have a 500 VA backup UPS for my computer. Whenever I switch ON my UPS it takes around 30 seconds to come to normal (to get Green signal), till then orange light will be emitted. I think UPS is in self-test mode at that time. Is it safe to switch ON my CPU and monitor or at least my CPU before...
  30. n.karthick

    Difference between ripple and harmonics

    Harmonics are integer multiples of the fundamental frequency. As far as electricity is concerned, the supply voltage and load current may have harmonics, if the electric load behaves non-linearly. For example, a diode or a thyristor is an non-linear element, they don't draw current all the time...
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