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power factor measurement for single phase supply at any power point ?


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#21 toprange

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Posted 05 August 2004 - 02:38 PM

Hi, mark

In your post in regarding of the PFC, you say PFC will not reduce kWh unless the copper loss is significant like the cable undersize or the lenght of cable is very long. Can you please tell me what's you estimation of the loss in real life like in a factory? 5%? 10% or 20%?

#22 toprange

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Posted 07 August 2004 - 02:17 PM

Any one will help me to answer my previous post? Thank you.

#23 marke

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Posted 08 August 2004 - 09:07 AM

Hello toprange

Cables are usually selected for a worst case voltage drop of less than 5%. This would suggest that the losses will be less than 5%, depending on the powerfactor of the load.
Short run cable voltage drop would be considerably less than this.

Best regards,

#24 Guest__*

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Posted 24 September 2004 - 02:23 PM

Being an HVAC tech I didn't understand the difference in what you were saying right at the start... ie: the difference between kVA and kW, and why power factor correction won't have any bearing on residential electric bills.

However, it's very clear now. (I think).

In industrial installations, when a motor wastes power generating a magnetic field, that power is not returned to the power source. (The power company). So if they supply a certain VA to the industial location, they receive less VA back. This is not hard to understand. The wasted power (especially in motors and transformers where there is a lot of heat and other waste, such as magnetic resistance) consumes power in large quantaties but doesn't do any useful work.

But in residential, that is not taken into account. (Tell me if I haven't gotten this yet). In residential -- if I understand correctly, in layman's terms -- the difference in lost VA is not measured. The power company doesn't care if your loads consume VA (possibly because there are too many residential locations and each one wastes too little, so the resources required to keep track of them all individually would be enormous, so what they do instead, probably, is just divide the overall lump residential cost of increased capacity required by the amount of residential customers and put it on their bill as a "transmission charge" or some such thing?)

However in industrial locations the difference is very noticeable, and costly to the power company, so they actually calculate the VA loss and bill for it.

It seems that they clearly know how many VA they are supplying, and how many are returning, from any given installation... they COULD do this with any given residential installation, however they just don't bother. They just bill pure usage.

Am I getting this straight?

#25 Guest__*

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Posted 06 October 2004 - 08:04 PM

How many microfarads in 1 KVAR???, is it 729??.

#26 marke

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Posted 07 October 2004 - 06:06 PM

The capacitor rating per KVAR is dependent on the supply voltage and frequency so there is not a standard figure for this.
The KVAR is the reactive current times the voltage. The current is the voltage divided by Xc (1/2 x pi x f x c)

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#27 Guest__*

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Posted 05 February 2005 - 03:06 AM

:mad:

#28 Guest__*

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Posted 26 August 2005 - 06:23 PM

hello Mark

please tell me what you think
If i was the GM of a rual electric coop wouldn't I want every member to have single or three phase true active pfc at there home or office.
This would allow for real savings to be relized by the owners of the coop,
the customers. Are you familier with capital credits, coop term for long term dividens. currant rate of return 1.8%. see what i'm getting at ?
phil bosco

#29 marke

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Posted 26 August 2005 - 08:54 PM

Hi Phil

If there was a definite power factor issue in the loads of homes and offices, then yes, but in reality, there generally is not so there would not be any advantage. You can only correct what needs to be corrected. To correct lights which have a power factor of 1 would be crazy. Diplacement power factor is caused by inductive loads, typically motors and the motor loading in these environments is a) intermittent, and B) generally small.

I would suggest that distortion power factor is a greater issue in these environments and that needs filtering, or needs standards to insist that appliences comply with appropriate standards. Much of the distortion power factor comes from rectifiers in electronic equipment and it is possible to use active rectifiers to ensure sinusoidal current, but it costs.

Best regards,

#30 Guest__*

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Posted 06 October 2005 - 06:31 PM

;qhi
i wanna know how can i use power factor coorection in my tv

#31 marke

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Posted 07 October 2005 - 04:29 AM

There are no motors in your tv, so you do n ot apply power factor correction capacitors.
There is a switchmode supply and you could use an active rectifier to reduce the harmonic distortion.
Best regards,

#32 Guest__*

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Posted 07 November 2005 - 07:26 PM

hello mark
i used a capacitor unit in my industry that reduced the bill by 33% cuz as i was told VA=W ,and any reduction in current will reduce the Wh ,my load was 700 amps by 380 and 1.73 its460 kva now its 455 amps with all my loads runing and 300kva bill .my meter uses 3 currents that sence the amps ,when i use external current meter i see 33% cut in current before and after the capacitor unit .when i caculate my current by 380 and 1.73 i get the same reading as my power meter is reading.finnaly cut in current redused my bill :)

#33 Guest__*

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Posted 13 November 2005 - 07:09 PM

;e;e;e any one here care to comment or tell me tips on why i had this cut in my bill?
;p;




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