Need Urgent Help : How to measure Power Factor

[zafir]

Hi, I know that there r already too much post on this topic.Our teacher has assigned us a project regarding PF.In this project i hav to measure PF and then display Its value further if it is lagging and below some value then automatically some capacitors would add in the circuit to make leading PF. I don't know frm where should I start + I also don't know about the technique of measuring it.
(i hav only worked on AT89C51 controller) Please guide me frm where and How should I start.I hav limited time for this project(approx 2 to 3 weeks).Please help me.thanx.
Regards,
Zafir.

 

[cameo_2007]

to put things in simple terms,

PF is the difference in voltage and current.
and that is nothing but the difference between the point when Voltage becomes 0 and Current Becoming 0. right?

so you need to find that difference in time between both occurences.

you should have two sections, one measure voltage and the other two measure current, with the out put of both going to different I/P port of the controller.

Now how to calculate the time.?
The controller should be continously monitoring these two signals.And WHEN the voltage becomes '0' ,start a TIMER and when the Current reaches its '0' values, stop that TIMER. so the timer value will give you the time gap between these two occurences, which is nothing but a relation of its Power Factor.

 

[zafir]

Thanku so much.I am working on single phase two wire (220 volt) circuit.So first of all I need something which reduces 220 volt to some smaller value so that it could be fed in controller via adc and then I hav to use small high watt resistor in series with load (now question is how much smaller the value of resistor should b selected) then voltage(this voltage would be in phase with circuit currrent) across resistor is digitized and then fed into controller.Please correct my mistakes.

 

[matbob]

Hi zafir,

I don't think you need an ADC. See the attached files for a simple solution.

 

[zafir]

Thanx

--
-
---
--
-
----
-
---
----
--
--
----

 

[juned73]

hey guys... even i got the same stuff to do..can u plz help me... i need to built a circuit for pf measurement that measures the pf of overall system..i m working on my major project "synchronization of multi (3) motors (a.c) using drives ,plc and HMI". in addtion to this pf mea... ckt. so plz help me...

 

[zafir]

Hi,I havent make any ckt of measuring pf until yet, if i get some stuff i will mail u.