measure reactive power using line volt and currents

[Coato]

Dear Sir/madam,

                           Hi i'm currently developing some kind of a power analyser, i'm pretty new to Labview i.e. complete basic tutorial so i'm encountering some problems at stage of measuring the reactive power.  I'm using a PCI-6052E card and developing my code in Labview 8.0.  I have attached a vi that I'm working on at the moment.  The idea is that my acquistion assitant will record my 3 phase voltage and currents coming in from 2 transducers circuit mainly for protection for the DAQ card, therefore I scaled them up in order to give me the actual values.  Then I want to delay the current siganls by a quarter of a complete wave in order to multiply with the voltage to give me the reactive power.  Then the rest of the code is getting a RMS rectified average value of reactive power.  So could any one suggest how I can perform the delay in order to get my reactive power measurement.  I would also want to find real power but i believe that's the same method except without the delay.  Please let me know whether i'm doing this right.  Thank you for your time.

Best Regards

Coato

[TroyK]

The easiest way I can think of to delay a signal is to change the t0 value. But this is a property of a standard analog waveform data type.
I don't know if there is a way to do it on a dynamic data type.

1. Set scales for each channel INSIDE the DAQ assistant (then you don't have to post process them afterward)
2. change data type to 1D array of waveform
3. add your quarter phase time to the t0 parameter of the waves.




Message Edited by Troy K on 03-04-2008 04:27 PM

[Coato]

Hi Troy,

           Thank you for your swift reply, I have try implementing your suggested algorithm and i understand the principles of the code.  However I seem to have some problems acquiring the desired signal and thats what i have been struggling on for the past few days.  I hope to get it sorted within these few days and then I will have a definite answer to whether it's wokring or not.

          Also, I have another problem that I hope you can help me out on, I have been asking another expert on another problem that i have been designing, it's title is 'measure rotor encoder signal' however the expert called Ian Colman who has been helping me greatly on it but hasn't replied to my recent problem for over a week and since im on a deadline to finish this project, is there any chance you can help me contact him or you can help on the topic, im not sure whether he's sick or off on holiday but i really need help on that topic and I would appreciate very much if you can find any help at all.  Thank you for your time.

Best Regards,

Coato

[Coato]

Hi Troy,

          Actually i have just got a reply from Ian there, sorry for the trouble.  I will update you once I have the power analyser up and running.  Thank you

Best Regards

Coato