Lewis Posted October 3, 2002 Report Share Posted October 3, 2002 Hello. Could anybody tell me how to measure the power factor without the power factor meter?I mean I want to make a circuit that can measure the power factor. Thanks ;q Link to comment Share on other sites More sharing options...
marke Posted October 3, 2002 Report Share Posted October 3, 2002 Hello Lewis Assuming that you are measuring the powerfactor of a circuit that is drawing a sinusoidal current, you can measure the power factor by measuring the angle between the voltage and the current. This is easily done using two comparators and an XOR gate. Use one comparator to monitor the voltage, giving you an output indicating the polarity of the voltage, and a second comparator indicating the polarity of the current. (the current can be monitored by the use of a CT) take these two square wave outputs and feed them into a XOR gate. The output of the gate will be a pulse stream with the mark space ratio indicating the phase angle, so you can filter this and measure the average level.If the current is not sinusoidal, than you need to measure the rms current and the rms power. Power factor = KVA / KW Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
Lewis Posted October 4, 2002 Author Report Share Posted October 4, 2002 Hello Marke The waveforms acquired from CT is analogue signal, how to convert it to digital signal (square wave)?Could you explain more about the comparators?Besides, have any other methods to measure the p.f. ? Do you know the "C/k value"? Thank you Link to comment Share on other sites More sharing options...
marke Posted October 4, 2002 Report Share Posted October 4, 2002 Hello Lewis Yes the output of a CT is analogue.A comparator is an electronic component, similar to an opamp that has an inverting input and a non inverting input and a digital output. If the inverting input is lower than the non inverting, the ouput is high. If the inverting input is higher than the non inverting input, the output is low. Have a look at the data for an LM339 and you will see more. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
mbitzer Posted October 22, 2002 Report Share Posted October 22, 2002 In another message I had seen......Power factor=kVA/kW but it should bePower factor=kW/kVA. Link to comment Share on other sites More sharing options...
marke Posted October 22, 2002 Report Share Posted October 22, 2002 Hello mbitzer,You are correct, power factor = kw/kvaBest regards Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
Guest Posted September 10, 2004 Report Share Posted September 10, 2004 is there any single ic chip to measure power factor Link to comment Share on other sites More sharing options...
Guest Posted December 10, 2004 Report Share Posted December 10, 2004 ;f;so, setting up a clock and a counter, counting when both U & I is positive, I can measure the p.f.? This means it is quikly to measure p.f. using soc, e.g. 8051. Why there is so many algorithm based on DFT to measure p.f.? Link to comment Share on other sites More sharing options...
marke Posted January 22, 2005 Report Share Posted January 22, 2005 Power factor comprises two components, displacement power factor and distortion power factor.In the case of a motor load, the power factor is essentially displacement power factor.Displacement power factor could be measured by using an 8051 to measure the percnetage of each cycle that the U & I are both positive. Distortion power factor would ned to have an analysis of the harmonic currents flowing. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
will Posted January 23, 2005 Report Share Posted January 23, 2005 Try this circuit it is made for singal phase the components are not hard to find,the more current you draw the bigger the wire.15a=14G wire. this is the site http://www.designnotes.com/CIRCUITS/pwrfact.htm Will Link to comment Share on other sites More sharing options...
Guest Posted January 23, 2005 Report Share Posted January 23, 2005 can i use 89c51 for power factor measurement...i am developing a circuit for power factor correction..can u suggest techniques for pf measurement using 89c51? Link to comment Share on other sites More sharing options...
Guest Posted January 27, 2005 Report Share Posted January 27, 2005 Anybody knows a circuit to measure power factor on 3phase motor?The circuit in the link http://www.designnotes.com/CIRCUITS/pwrfact.htmis just for one phase!Instead of current transformer can I use hcpl-788j? Link to comment Share on other sites More sharing options...
marke Posted January 27, 2005 Report Share Posted January 27, 2005 Use the same circuit for each phase, (three circuits) and combine the outputs. You need a Current transformer to mearsure the current. An opto isolator will not carry the current. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
Guest Posted January 27, 2005 Report Share Posted January 27, 2005 What current transformer should I choose to support a current of 15.9A at 400VAC (3phase - I leave in Portugal and F-N it´s 230VAC). The current transformer with ratio 1:1000 that´s oK? You said that I had to do the same circuit in each phase (I supposed that) but I only need one current transformer, that´s right?!In each comparator I have to supply them with current and voltage... The current we use current transformer and the voltage we supply directly,passing by resistances, the Amp-Ops?Just one more question... and if we haven´t Neutro (just 3phase) how we connect the circuit?Thank´s!Regards Link to comment Share on other sites More sharing options...
Guest Posted February 22, 2005 Report Share Posted February 22, 2005 yea hi just been thinking abut it and i dont axually know why i can never get my power factor to 1. it sits at the mo @ 0.96 but i can get it no closer. out of intrest any one know why that is or wat i can do to get it higher cheers willie Link to comment Share on other sites More sharing options...
marke Posted February 22, 2005 Report Share Posted February 22, 2005 Hello willie If the power factor is purely displacement power factor, then you can in theory correct it to 1 provided that you have small enough steps in your capacitor bank. Three possible reasons for not getting to 1.0 are:1. Poor power factor less than 1 due to presence of distortion (or harmonic) power factor.2. Meter not accurate around 1.03. Capacitor steps not small enough. If you add too much cpacitance, you will go from a lagging power factor less than 1, to a leading power factor less than 1. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
Guest Posted February 23, 2005 Report Share Posted February 23, 2005 yea i think that the meatre is slightly off... however was chating with a mate in the electricty board he came to a conclusion that for some strange reason (in real life senairos) that it is imposable to get 1... any thoughtscheers Link to comment Share on other sites More sharing options...
chives Posted February 23, 2005 Report Share Posted February 23, 2005 i am studying PFC as part of an engineering services surveying degree.can anyone spare me 10 minutes to review a question that i am completely stuck on. my email address is lionel.hives at cyrilsweett.com cheers Link to comment Share on other sites More sharing options...
marke Posted February 24, 2005 Report Share Posted February 24, 2005 Hello chives Post your question in the student section and we will look at it. - we do not do your homework for you, but will offer some guidence as to how to solve the problem.I have edited your email address. I recommend that you do not post complete email addresses with the '@' because these addresses will be collected by automatic spam spiders crawling the web and you will get loads of spam. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
Guest Posted February 26, 2005 Report Share Posted February 26, 2005 hi, I am also studying/making energy power saving device for single phase.is it possible to use capacitor to 200W heater coil that is use in my incubator.I have 9 doors of incubator having 400W heaters each doors.or can i used thyristor unit to breakdown my electric bills?pls help, any suggestion pls..... Link to comment Share on other sites More sharing options...
Guest Posted February 26, 2005 Report Share Posted February 26, 2005 by the way i am junior, tnx..... regards....;p; Link to comment Share on other sites More sharing options...
Guest Posted March 28, 2005 Report Share Posted March 28, 2005 I would ask how far is purely transmition line can affect of the cost of power factor in an industrial firm?i mean if i received 0.95 from transmition line is the same cost for correction capacitor bank if i received poor 0.6 pf?best regards;) Link to comment Share on other sites More sharing options...
marke Posted March 28, 2005 Report Share Posted March 28, 2005 The power factor of the transmission lines has no effect on your load. When you measure the power factor at your point of supply, you are only seeing the power factor of your plant. You can not see the power factor of the transmission lines.A poor power factor on the transmission system will not affect your firm. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
Guest Posted March 29, 2005 Report Share Posted March 29, 2005 thank you mark for yr quick reply, i am greatly appreciated your heigh quality of great experience you got on the long past years.best wishesabbas:D Link to comment Share on other sites More sharing options...
Guest Posted March 30, 2005 Report Share Posted March 30, 2005 Hican u tell me how can i use 89c51 for my power factor measurement and control? Link to comment Share on other sites More sharing options...
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