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Hello friends , I am using Myrio to measuring three current values and three voltage values. My goal is clacular the power factor. I am using in the program "Electrical Power Suite". My problem is this I need to know if someone can send me an application example. I'm getting three 180VP voltages and Transforming for 1 ~ 4 V and playing the analog inputs (stage RS and T) and three voltage values leaving the current sensor, in a range of 1.5 to 3.5 V (- 5A 5A). What I need to know is how to set up the program to the transformation of these values and play the power factor calculation block. Someone please help me? I have a period of six days. Thank you for your attention
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Message 1 of 10
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Since noone else is answering, I will give you an advice.

 

Not sure if it is only me, but I guess the others do not really understand what you want, too. But I will give it a try.

 

So, you have a myRIO and you are measuring 6 analog voltage signals (3 of them can be used to calculate the current, using a given resistor value).

 

The "current sensor" has an output range from 1.5V to 3.5V? The other "voltage sensor" has an output range from 1V to 4V?

Using U=R*I and P=U*I will give you the power. But I guess you already know this and you want to know how to get the measured voltage values.

 

The fastest way is the following.

1, Create a new project in LabVIEW (use the myRIO template, the myRIO has to be connected to the PC via USB)

2, Add a new target (which is the myRIO) (I am not sure, but I guess if you use the myRIO template, the myRIO is added as a target automatically)

3, Right click on the target --> New --> VI

4, If you have done all correctly, you can choose "myRIO" in the function palette

 

For a first try, you can use the express VIs to read the voltage of several ports, there are several examples given by LabVIEW. You can find them if you click on the "help" tab on the frontpanel / blockdiagram ---> Find examples... A new window opens, here you can search for myRIO examples.

 

hope this helps a bit

 

kind regards

slev1n

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Hello friend, thanks for listening, Hello friend, thanks for listening, Sorry me for not being clear. My system is three-phase. To measure the current values, I am using three ACS712-05B sensors, the current range is 5A to 5 A. The value it provides is in the range of 1.5V to 3.5V. When the current is 0 A, the voltage value that the controller will read is 2.5V. I'm measuring 3 current values. To measure the three voltage values ​​(URN-USN-UTN) I used a transformer 120:1 , the primary value of the voltage is 180V~ and sub is 1.5V~. The analog input of the Myrio is from 0 to 5 V, so I did an adder circuit with an operational amplifier, then the value you got is from 1 to 4 V. I plan to measure the power factor in this three-phase system. I have the "Electrical Power Suite" library, but I'm not knowing assemble the program. The only examples I found were with the DAQ Assistant.  With this information, it became clearer my intention? again, thank you for help, if necessary, I send files and photos I have. ps: I have only five days in order to complete this project
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Solution
Accepted by topic author Davi08

So you need help to read the voltage values with your myRIO.

 

Since I have no knowledge about your electrical power suite library, I can only recommend you, to follow my instruction. Create a new project with myRIO template (I think if you connect your myRIO with your PC a window pops up, giving you the option to create a new myRIO project). Than you can use the myRIO library which you can find in the function palette. Using the express VIs at the beginning is very easy, later you can use the normal VIs to read all the analoge voltages from different analog ports.

 

Hope this helps

 

kind regards

Slev1n

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Message 4 of 10
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Again, thank you for your attention! How would you analyze the power factor of a three-phase system? Do you have any examples? I have to read the analog inputs three voltages and three currents. I can read these values, but I think there is a way of treating these signs so that I can get the values of the active power, reactive power, apparent power and power factor.   Best regards Davi
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Please, Look at the attachment, I sent a picture
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Message 6 of 10
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Solution
Accepted by topic author Davi08

Well, according to your picture, you already managed to read in the analog voltage values. The first step is done.

 

I have to confess, that I am not that familiar with the 3 phase system. But after some "google" I have found the following formula:

 

P1= Sqrt(3) * U1 * I1 * cos(phi); cos(phi) = power factor (some examples for power factos are here: Power factors)

 

P total = P1+P2+P3

 

I am a bit confused with cos(phi), not sure if its just a power factor, or if it is the phase of the sinusoidal voltage of one strand of the three phase system.

 

Maybe someone being more familiar with that can help from here?

 

kind regards

Slev1n

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Message 7 of 10
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Hello friends, I'm doing a project with Myrio. I am looking to make the power factor of the analysis of a three-phase system. For this, I am using three sensors (ACS712 05B) for measuring the current values and set up a circuit to transform the three voltage values (180 ~ v phases R, S, T) for 1 to 4V (because my analog input is 0 to 5 V). Does anyone have any examples of power factor measurement? (I think the DAQ Assistant does not serve). The problem I'm having is that RMS values are varying constantly, and the power factor is negative (using resistive loads only). Can someone help me please? Thanks for listening Best regards David
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Solution
Accepted by topic author Davi08

there is the electrical power suite available for download that could help you

 

http://www.ni.com/white-paper/8652/en/#toc3

 

without using it, to calculate the power factor i would do:

 

1. take the Voltage signal and the Current

2. do an FFT over each

3. limit results samples to an observation period (not larger than the waveform)

4. convert in complex arrays 

5. take Real part to find peak indexes

6. use index to catch the phase value -> then difference-> then cosine

 

as in the attached picture.

 

hope this helps

m.

 

 

 

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Message 9 of 10
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I am very grateful for your help, this example helped me a lot.


Please Could you send me an example with three voltage signals and three current signals? My circuit is three-phase

 


Best regards

David

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