How to simulate reactance in LabView

[sod mala]

Hello,

I am new to LabView.

I am trying to apply PWM (Pulse Width Modulation) wave with fundamental frequncy of 50Hz to Inductor of 10mH, to find out frequency response across Inductor.

No of samples used for PWM generation are 10,000.

I am able to get response to any particular value of F, by using mathematics toolset, but I am not getting how I can get accumulated output across inductor for all frequencies in PWM signal.

Any inputs?

[Pnt]

I am not sure that i understand.

Is it  a sine wave?

Do you want to add the signals so you will have a new signal, with many fundamental frequences ?

If so, just add the signals....

[hrh1818]

On Mar 31, 6:10 am, sod mala <x...@no.email> wrote:
> Hello,
> &nbsp;
> I am new to LabView.
> I am trying to apply PWM (Pulse Width Modulation) wave with fundamental frequncy of 50Hz to Inductor of 10mH, to find out frequency response across Inductor.
> No of samples used for PWM generation are 10,000.
> &nbsp;
> I am able to get response to any particular value of F, by using mathematics toolset, but I am not getting how I can get accumulated output across inductor for all frequencies in PWM signal.
> &nbsp;
> Any inputs?

From my interpretation of what you are trying to do it sounds like you
could accumulate your 10,000 data points in an array. Once the data
is stored in an array you could either plot the data to see a graph of
the data or do a discrete Fourier transform on the data to see the
amplitude of frequency spectrum.

Howard

[CarlaU]

Hi sod mala,

Can you explain your setup a bit more? Are you using a DAQ card for the PWM or are you using a R series card? There are some great examples in the NI Example Finder for both setups. Go to Help»Find Examples. In the search tab, type PWM. You will then see a few great examples show up in the middle pane. If you are using FPGA, then you can also find some examples at the IPnet site under Data Acquisition category. I hope that helps!

Carla

[sod mala]

Hi All,

Thanks for response.

Well, I am trying to simulate effect of inductive load on square wave.

Basically, Square wave has got number of odd harmonics of fundamental frequency. And as Inductance is 2*pi*F*L, it wil act as low pass filter.

So, I want to show by using only LabView software (without any hardware), frequcny spectrum of voltage before applying to Inductor and frequncy response of current through inductor. I expect that current will have not have lot of high harmonics in it's specturm.

I am facing problem to simulate inductive load. How I can simulate 2*pi*F*L, as I am nopt checking for particluare F value but all spectrum.

Should I convert first all signals in Fourier domain? 

[Vikas_K]

As far as I can think, you will have to find the transfer function of the inductance in time domain and then use that equation to simulate.

Vikas

[Pnt]

---

sod mala wrote:

as I am nopt checking for particluare F value but all spectrum.

Should I convert first all signals in Fourier domain? 

---

I think yes. You do not have to check the entire spectrum. Only enough harmonics, to give you a result.

If you check for the first 20 harmonics you will be ok.

[hrh1818]

On Apr 2, 5:10 am, sod mala <x...@no.email> wrote:
> Hi All,
> Thanks for response.
> Well, I am trying to simulate effect of inductive load on square wave.
> Basically, Square wave has got number of odd harmonics of fundamental frequency. And as Inductance is 2*pi*F*L, it wil act as low pass filter.
> So, I want to show&nbsp;by using only LabView software (without any hardware), frequcny spectrum of voltage before applying to Inductor and frequncy response of current through inductor. I expect that current will have not have lot of high harmonics in it's specturm.
> I am facing problem to simulate inductive load. How I can simulate 2*pi*F*L, as I am nopt checking for particluare&nbsp;F value but all spectrum.
> Should I convert first all signals in Fourier domain?&nbsp;
> &nbsp;
> &nbsp;

The basic or full versions of Labview are not suited for simulating a
square wave voltage source connected to an inductor. Other tools like
SPICE and National Instruments add-on Simulation module for Labview
are better suited for simulating a square wave voltage source driving
an inductor. Then there is always the old fashioned way of converting
a square wave to a Fourier series and dividing each harmonic of the
series with the impedance of the inductance at the harmonic frequency
to determine the magnitude of the current at each harmonic.

For a 50% duty cycle square wave with an amplitude of plus and minus 1
and no DC component the components of the harmonic series are equal to
zero for even harmonics and are equal to 4/(PI*n) for odd harmonics.
Therefore the magnitude of the current at each odd harmonic is 4/
((PI*n)*|j*w*n*L|).
Which is equivalent to 4/(PI*n*n*w*L). PI = 3.1459, n is the nth odd
harmonic, w = 2*PI*f Or 2*PI/T where f is the fundamental frequency
and T is the period of the fundamental frequency. L is the inductance
in Henries.

There is a very clever demonstration of Fourier series at:
http://www.falstad.com/fourier/
You can use the demo to see what the amplitude oft the harmonics will
be for duty cycles other than 50%. Note you need to have Java
installed on your computer to see the demo. The demo runs runs
flawlessly with Firefox. The page also has links to clever
demonstrations of numerous technical subjects.

Howard