Measure power factor using 89c51

EDAboard.com Forum Index -> Microcontrollers -> Measure power factor using 89c51

Author

Message

lats

Joined: 27 Oct 2005
Posts: 199
Helped: 7

29 Apr 2007 6:06 measuring power factor

Hi friends,
i trying to measure power factor using 89c51 but the results are not stable. i simply started timer on first interuppt and stopped on second and then caculated, but the results aren't too good. i mean they are not too stable some times they show proper value sometimes wrong.
can anyone please share some code for the same.

Thanks

With best regards.

nandhu015

Joined: 11 Feb 2006
Posts: 641
Helped: 46
Location: Tamilnadu, India

01 May 2007 14:40 how to measure power factor

Hai

As far as i know measuring power factor is not an easy job.

And further more 89c51 is not suitable for that job.

Nandhu

Here is something i found on another forum
http://avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=49317&highlight=power+factor&sid=58b096183ad3eb0385ad108f9725fb83

pravin_dwaramwar

Joined: 06 Dec 2006
Posts: 121
Helped: 3
Location: Nagpur - India

02 May 2007 15:50 measure power factor

Dear friend will u tell me ur scheme of calculating PF.
then only i can help u.

sawaak

Joined: 20 May 2003
Posts: 153
Helped: 4

02 May 2007 17:19 microcontroller power factor

Hi,
check the following post

http://www.edaboard.com/viewtopic.php?t=195002&highlight=power+factor+8051

thanks
sawaak

muoinhohn

Joined: 05 Nov 2004
Posts: 211
Helped: 1
Location: Hanoi

06 May 2007 5:25 measuring power factor microcontroller

Hi lats,
How do you calcul power factor with 89C51? If you describe your problem in detail, then people in the forum can help you.
I think if you measure simply in detecting the zero cross of I and U , after calcul the duration, then PF is not correct.
Regards
Muoinho

roykyn

Joined: 15 Sep 2006
Posts: 254
Helped: 7

06 May 2007 18:35 power frequency zero crossing

one simple method of finding the power factor is by using pll......
check cd4046 IC .....

jayavardhan

Joined: 01 Sep 2006
Posts: 125
Helped: 3
Location: India

07 May 2007 9:15 power factor microcontroller

As far as i know measuring power factor is not an easy job.

donot use normal timers use a timer which is having a PWM mode.

lipeng

Joined: 29 Apr 2007
Posts: 3

08 May 2007 9:37 measure power frequency

use a small dsp

muoinhohn

Joined: 05 Nov 2004
Posts: 211
Helped: 1
Location: Hanoi

09 May 2007 7:19 measuring power ic

You can use 89C51 incorporate with ADE77xx (7753 , 7754...) of Analog Devices.
Regards

lats

Joined: 27 Oct 2005
Posts: 199
Helped: 7

09 May 2007 11:11 measuring power factor: problems

lipeng can u please guide me which small dsp can i use.

muoinhohn, few month back i tried lot interfacing ADE7754 with 89c51 but wasn't able to do it. can u share some code regarding the same.

Thanks all of you

watermelon

Joined: 08 May 2007
Posts: 77
Helped: 8

09 May 2007 15:50 50hz counter with 89c51

I guess, the problem is that there are

(a) Initial errors due to the analog hardware etc. causing phase shift, error in zero crossing etc. leading to repeatable errors which can be nulled by calibration.

(b) The frequency is not always 60/50 Hz, it varies.

(c) Noise and interference.

I'd suggest :

(a) Get the current sample, filter (amplitude limiting is also required) and use a zero crossing detector to get a zero pulse on rising (or falling) edge.

(b) Do the same with voltage.

(c) Use the interrupts on the microcontroller to count the phase, i.e. start with voltage zero and end with current zero, continue counting till the next voltage zero, this gives you the 360 degrees of the voltage (indicating exact frequency). Phase error due to power frequency changes will be small and may be ignored unless you want higher accuracy (than normal), in that case, calibrate for each increment / decrement of 1 or 2 Hz..

(d) Divide phase count by frequency count. First calibrate with known zero phase shift (at the specific power frequency) and find the error. Ensure that nothing heats up.

(e) From each count subtract the error in real readings. Integrate over 16 or 32 samples to get an average value.

The counter frequency should be sufficiently high to provide the required resolution. You could use 60 (or 50) X 256 (8 bits, but keep the counter as 16 bits in case of decrease in power frequency) = 15,356 Hz. 8051 and derivatives have no problem at this count rate.

Use noise / RFI filtering and enclose everything in an earthed metal box. Use very good grounding.

This worked 10 years ago.

watermelon

Joined: 08 May 2007
Posts: 77
Helped: 8

11 May 2007 9:54 measuring power factor

Of prime importance is ensuring that interference, high voltage, spikes, current surges etc are removed. This requires good signal conditioning and careful designing.

I guess, sampling once every second and using a window filter of 32 samples should be sufficient. Surges due to heavy machinery start / stop / load / unload range from 2 to 15 seconds. Filter length and sampling rate can be modified to suit various needs.

I hadn't tried median or modal filters, but these could be easy to implement in software.

Google
AdSense
Google Adsense

11 May 2007 9:54 Ads

mg_designs

Joined: 08 Jun 2007
Posts: 19

08 Jun 2007 8:35 how do i measure power factor

i measure power factor with ade7754 the result was very good

Prabakaran

Joined: 22 Jan 2007
Posts: 160
Helped: 5
Location: Chennai(India)

13 Jun 2007 15:00 how to measure power factor?

Measuring The Power Factor is not So easier Thing.

Better Go for Accuracy Meter ADE7753 which is single Phase Power Meter IC .
In That measure the Watt and VA energy wit those parameters calculate the Power factor. But ADE7753 supports SPI protocol to access the data from that. Better GO for AT89S52 which supports the SPI protocol .

hulahula

Joined: 15 Jul 2006
Posts: 33

23 Jun 2007 19:01 measuring power in microcontroller

http://www.c51c51.com/index.php?lay=show&ac=webboard

svaidy

Joined: 09 Aug 2009
Posts: 10
Location: Thanjavur

11 Sep 2009 16:03 power factor measurement mcu

Please tell the circuit for power factor measurement for 1-phase circuit. and please give the circuit diagram and codings for microcontroller. This will very helpful to our project.

thanking you,

with regards,
S.Vaidyanathan,
srivenkatraman(at)gmail.com