Rogowski Coil Current Monitor.

Discussion in 'The Projects Forum' started by Ungkuiskandar, Feb 12, 2009.

  1. Ungkuiskandar

    Thread Starter New Member

    Feb 12, 2009
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    0
    Hi guys, im new to this forum, so please do bear with me if im doing something wrong.

    Anyway, For my third year project, i have been assigned to design build, and test a rogowski coil current monitor. I have been reading lots of articles about it and been trying to understand it, so if any of you who is quite familliar with it, please do assist me in understanding the main concept and design and such. Please do correct me if im wrong about the R.Coil


    For those of you who's wondering what it is, it's actually works like a current transformer which is used to measure current from electronic devices.
    The idea is to use a non magnetic core, which u get a coil to wrapped around it, where both ends meet and connected to a circuit intergrator to measure and current from any device.

    HERES THE QUESTION----> i am currently working on the electronic integrator which uses Op-Amps. I need help DESIGNING e.integrator and the calculation required for it.

    I have chosen,
    input current,I = 10A - 10 ma range and
    output V = 10V - 10 mv.

    I am not sure about the frequency range and also the rest of the required parameters. Also i have not chosen a specific application for it, but it should somehow fit in that criteria.

    Any ideas on how to solve this guys?

    Thanks very much
     
  2. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    Do you have to use opamp? There are power metering IC that can be interfaced to rogowski coil available. See AD line of power metering products.
     
  3. Ungkuiskandar

    Thread Starter New Member

    Feb 12, 2009
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    0
    im not sure if i have to use op-amp. i assumed that electronic integrator consists of op amp by reversing the resistor and capacitor configuration to obtain and op amp integrator?...im not sure myself...i use this as reference.

    http://homepage.ntlworld.com/rocoil/principle.htm

    and what do u mean by power metering IC? can u please explain what does the integrator actually do? Is it because the coil winding will induce EMF and generate voltage thus needing the integrator to change it into current?
     
  4. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    Integrator sums up the values overtime. Because the output of rogowski coil proportional to change in current overtime (di/dt), to get the actual value of current an integrator is needed.

    If you have to use opamp, then, yes, you need to design an integrator using an opamp. However, AD, and other manufacturers out there, have power metering IC that can be interfaced directly to rogowski coil, and will output various values such as real power, apparent power, etc. in different format (pulses, serial, etc.). It is much easier for you to just use one of these IC instead of designing your own integrator.

    Have a look at this page http://www.analog.com/en/analog-to-digital-converters/energy-measurement/products/index.html
     
  5. Ungkuiskandar

    Thread Starter New Member

    Feb 12, 2009
    3
    0
    hi guys. Is it possible if any of u could give me advice online? I have built my own rogowski coil using a 75 ohms co-axial cable about a meter long.

    I have wind it up using a wire and turn in 282 times around the coil. I plan to use it for instrumentation purposes.

    The voltage range that i have decided is = 1mV - 10V
    and operating current range to be = 1mA - 1A.
    the frequency range should be about = 1Hz - 1kHz

    i have then make my own calculations, to get the integrator value, which is

    Calculations
    E = H di/dt
    H= munaught N A
    N= 1762.5 turns/m
    Radius of the coil = 2 x 10-3
    Cross sectional Area A = Pi r^2 = 1.26 x 10^-5
    Mu naught = 4 pi x 10^-7
    So H = 27.9 nVs/A --------- coil sensitivity

    Say Vout = 10 V, I = 1 A

    then

    Vout = IH/CR
    CR = 27.9/10 = 2.79
    If R = 10000 ohms, then C = 2.79/10000 = 0.000279 F = 279 x 10^-6 Farad

    does that makes any sense ?

    also yesterday i tried my soundcard as an integrator to produce waveform using soundcard as a DSO. I used winscope and online oszilloscope but to no avail. I couldnt get it to work.

    I have got pictures of my coil and everything. If any of u r interested i could email it to you, then maybe u could help me figure out what went wrong.
     
  6. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    I notice this older post was revisited by OP.

    Are you still in need of advice Ungkuiskandar?
     
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