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Single Phase Power Factor Correction


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Hello tinku


Welcome to the forum.


You can certainly power factor correct single phase loads, but you will not save any KWHrs by doing so.

There are a number of suppliers of domestic "energy savers" that are just a power factor capacitor, and some of these suppliers claim substantial energy saving from their usage, but the reality is that if there is a poor inductive power factor, the current can be reduced, but the KW can not.


As has been stated many times, you will only benefit from power factor correction if you are paying a penalty for poor power factor. This may be a power factor penalty, or a KVA maximum demand penalty or similar.

You do not pay these in domestic situations, only larger industrial installations.


Best regards,

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  • 4 months later...

just wanted to clarify about this.


at poor power factors, in applications that require constant amount of power, there will be an increased current (P=V*I*PF, PF goes down I goes up to maintain power and vice versa)


could it be possible that the energy saving claims refer to I^2*R losses?


i understand that there will be no reduction in KWhr because you arent reducing the power. and copper losses in a residential application should be near insignificant (due to low resistance).


of course could be entirely wrong with this, but im 90% sure of my theory

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No, you are essentially correct, but the problem is, i2r losses are, as you point out, relatively low in a motor and can be reduced in an installation by simply using the proper sized conductors. In other words, if they show energy savings from reduction of i2r losses in an installation, chances are the conductors were undersized to begin with.


The reductio of i2r losses does show up in the main utility power distribution system, but any 1 phase residential installation is insignificant to the total and in fact, even large groups of residential users don't amount to enough for utilities to worry about.

"He's not dead, he's just pinin' for the fjords!"
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