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LDmicro Forum - power factor project

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power factor project (by Ibrahim )
can any body give me an example to calculate power factor by ldmicro
Wed Mar 20 2019, 13:31:37
(no subject) (by Ziggy)
Do you know what power factor is?
Do you have any experience in measuring power,voltage and current?

The actual calculation is simple enough once You have power, voltage and current .
Wed Mar 20 2019, 15:53:26
power factor project (by Ibrahim )
hello Ziggy
thanks for reply yes calculation of voltage is easy I will take it as analog value & scale it 0-5 v to 0-1023 and take signal from current transformer ie 1 A and change it to volt by a resistor so I can deal with it that's nice but the problem is how can I deal with angle between voltage & current( converted voltage) which is called cos_angle
p=IV cos_angle(I-v)
Mon Mar 25 2019, 01:33:07
(no subject) (by MGP)
You cannot do this with LDmicro because of the cycletime, it's too slow and has no math.

But look at this https://www.instructables.com/id/How-Measure-AC-Power-Factor/
Mon Mar 25 2019, 03:05:01
(no subject) (by Ziggy)
Hello Ibrahim,

That is the real problem. How to measure real watts as opposed to Voltamps.

Analog devices have a chip whihc does just that.
Measures real power VIcos ( phi)

The other option is to in LDmicro set up two AtoD measurements paths at the top of the ladder.. the very first thing the ladder does.



This way you can be assured of quite precise timing of measurement ( nothing else happens before the conversion so no chance of variability in timing.

Build an operational amplifier buffer which will scale the voltage and current signals around half the microcontroller supply ( 2.5 volts.)

Do say 90 samples a second,that is to say make your ladder cycle time 11.111miliseconds.

Start sampling the voltage and current waveforms.
Set up a counter and initialise it to zero.

use voltage as the phase zero reference and check the voltage value to be 2.5volts plus or minus a small deviation.
When voltage sample = 2.5V voltage is at zerophase.
Start the counter to increment
check current value like you did voltage level. iWhen current value =2.5v counter stops counting.

Counter content is proportional to phase difference. Measure voltage rms and current Rms values and You know everything about the single phase load.

Read up on sampling undersampling and oversampling to figure out maths of the problem.
Mon Mar 25 2019, 03:13:48
(por Ibrahim) (by Calubert)
Hola creo que si usas una entrada analógica y haces una salida PWM tendrás la respuesta. y la salida la vuelves a hacer en una nueva entrada analógica. de esta manera sabrás el voltaje real ya que tienes una escala de 1023, según el micro de voltaje 2,5v o 5v. =1023 dividido 2,5 = 409 posiciones de le imagina.
Tue Mar 26 2019, 05:00:14
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