# Power Factor Measurement( How To Obtain The Current?)

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### #1 fancy102

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Posted 23 November 2007 - 04:02 AM

hi..I would like to construct a circuit that can measure the power factor of a system. I would like to use comparator, analogue switch and PIC controller to measure the power factor..the output of the analogue switch is voltage(analogue form)
So,my problem is how to measure the current of the system so that i can get the voltage and current to measure the power factor?thanks

### #2 marke

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Posted 23 November 2007 - 05:30 AM

Hello fancy102

Welcome to the forum.

Have a look at Power Factor Measurement
Does this help??

Best regards,

### #3 fancy102

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Posted 24 November 2007 - 09:10 AM

yaya...thanks a lot!!it does help but i still facing problem...

if i constuct a circuit as shown..then where should i measure the current?the OP-AMP already change the current into voltage form..

my question is if both of my control signal n input into the anlogue switch(4066) are voltage......then where to get my current?
thanks for helping..ur kindness are really appreciated...

circuit are:

output of OPAMP 356 become input into comparator(V) }become input of analogue switch(input signal)
+
ootput of compatar(V) } become input of analogue switch (control signal)

### #4 marke

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Posted 24 November 2007 - 09:37 AM

Hello fancy102

To measure displacement power factor, you need to measure the angle between the voltage and the current and the easiest way to do this is to create a square wave that is representative of the polarity of the voltage waveform, and another square wave that is representative of the polarity of the current waveform. - you do not need to measure that actual voltage or current, just the angle between them. You can use an XOR gate to combine the waveforms, or you can use a timer in a micro to measure the time between the positive transitions. You could then output this as a PWM waveform and filter to get an analogue output.

If you are looking at measuring more than just power factor, then the output of the CT can be monitored by additional circuitry which can give you the current magnitude.
If this is not what you are looking for, then please explain what you are looking for and why so that we fully understand what you want and we may be able to help.

Best regards,

### #5 fancy102

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Posted 30 November 2007 - 04:24 PM

Dear marke,

thanks for your guidance..i had some idea about the measurement...

so,what i need to do is just measure the phase (angle of current and voltage)...then through programming ( PIC )my output will send to the LCD display...

ok..really thanks for helping..

### #6 keoshiro

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Posted 20 February 2008 - 09:21 AM

hello fancy102,

### #7 keoshiro

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Posted 20 February 2008 - 09:31 AM

QUOTE (keoshiro @ Feb 20 2008, 05:21 PM) <{POST_SNAPBACK}>
Hello fancy102,

Currently, im doing a project on power factor correction that is similar to yours and now facing some problems. Actually, i planning to use a current transducer, comparator, phase detector and capacitor banks to design the project but facing many problems. Do you mind share with me about your circuit design so i can take it as a reference?
Here is my msn, keolim85@hotmailcom, and my email is caesarlim85@yahoo.com

I would appreciate to hear from you, thanks.

### #8 far8z

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Posted 25 July 2008 - 07:40 AM

QUOTE (fancy102 @ Dec 1 2007, 12:24 AM) <{POST_SNAPBACK}>
Dear marke,

thanks for your guidance..i had some idea about the measurement...

so,what i need to do is just measure the phase (angle of current and voltage)...then through programming ( PIC )my output will send to the LCD display...

ok..really thanks for helping..

Currently. i'm doing my final project on how to measure power factor using PIC microcontroller...now, i'm having problem in designing the circuit on how to measure the PF..So, would you mind to share with me about your circuit design so i can take it as the reference?..your help is appreciated...

### #9 far8z

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Posted 25 July 2008 - 08:15 AM

hi fancy 102;

Currently. i'm doing my final project on how to measure power factor using PIC microcontroller...now, i'm having problem in designing the circuit on how to measure the PF..So, would you mind to share with me about your circuit design so i can take it as the reference?..your help is appreciated...

### #10 far8z

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Posted 25 July 2008 - 08:25 AM

QUOTE (far8z @ Jul 25 2008, 04:15 PM) <{POST_SNAPBACK}>
hi fancy 102;

Currently. i'm doing my final project on how to measure power factor using PIC microcontroller...now, i'm having problem in designing the circuit on how to measure the PF..So, would you mind to share with me about your circuit design so i can take it as the reference?..your help is appreciated...my email is far8z@yahoo.com

### #11 x20a

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Posted 29 September 2009 - 12:39 PM

hi, i'm also currently doing my final yr project which is correcting the power factor in houses.
so i followed the step in reading the power factor found in this forum which convert the sinusoid of voltage and current to a square waveform
i'm using op-amp (lm324) to convert the sinusoids
the problem is the square waveform will be distorted when the magnitude of voltage grows larger than 1 V
is there any solution for this problem??

### #12 marke

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Posted 29 September 2009 - 05:34 PM

If you are using the op amp as a comparator to produce a squarewave output that indicates the polarity of the input, it will not become distorted by a change in input voltage provided that the input voltage does not exceed the supply rails. This can be prevented by using diode clamps.

Best regards,
Mark.

### #13 x20a

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Posted 01 October 2009 - 03:01 AM

QUOTE (marke @ Sep 30 2009, 01:34 AM) <{POST_SNAPBACK}>
If you are using the op amp as a comparator to produce a squarewave output that indicates the polarity of the input, it will not become distorted by a change in input voltage provided that the input voltage does not exceed the supply rails. This can be prevented by using diode clamps.

Best regards,
Mark.

thx for your reply mark.. hm then i got another question, where do we have to clamp the diode on the circuit??
thx in advance and really appreciated it

regards,
x20a

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