"Real" Power or "True" Power

Status
Not open for further replies.
D

Do You Like Ham

Member
Location
TX, USA
Hi-

Does anyone have any interesting insight into the terms / application of "Real" vs. "True" Power? AFIK, they're completely interchangeable.. is there any industry preference one way or the other? Does the NEC favor one or the other. I had hoped to find a simple answer in the definition of Power Factor.. the 2005 NEC I have pointed to Annex D, where it defines Power Factor as: "Calculations in the following examples are based, for convenience, on the assumption that all loads have the same power factor (PF)"... so that wasn't fruitful.
 
Do You Like Ham said:
Hi-

Does anyone have any interesting insight into the terms / application of "Real" vs. "True" Power? AFIK, they're completely interchangeable.. is there any industry preference one way or the other? Does the NEC favor one or the other. I had hoped to find a simple answer in the definition of Power Factor.. the 2005 NEC I have pointed to Annex D, where it defines Power Factor as: "Calculations in the following examples are based, for convenience, on the assumption that all loads have the same power factor (PF)"... so that wasn't fruitful.
Click to expand...
Real = True

PF = KW / KVA
 
In my circles, “true” or “real” power was simply referred to as “power”. The KVA of non-unity power factor loads was always called “apparent power.”
 
Real and true are the same thing.

NEC doesn't really have any definition for this sort of thing, NEC doesn't really get too involved in actual power factor calculations, just has rules on how to install correction devices and similar items. Sizing them (as in determining how many kVAR is needed) is outside the scope of NEC.
 
The only thing I can think to add is in relation to measurement equipment that there is a difference between "power" and True RMS Power. They are the same only for sinusoidal voltage/current waveforms. An engineer would say that the RMS power is "implied" when saying real power, but cheaper meters say they give you power readings only for sinusoids.

Mark

Mark
 
zbang said:
FWIW, I don't think I've heard of someone using "true power", it's always "real power" for watts and "apparent power" for KVA. Might depend on local custom.
Click to expand...
I had a boss who grew up and studied in South Africa, he referred to it as "True" power and argued with us lowly 'Mercan underlings that calling it "Real" power implied there was such a thing as "Unreal" power. I countered that his position then implied the existence of "Untrue" power too. We agreed to disagree...

Since then I have casually observed that most people I have discussed this with here in North America refer to it as "Real", but I see a lot of articles referring to it as 'True". I have no idea where that came from. I just looked in a couple of international electrical glossaries I have to see if it maybe came from translations, they were no help. Some said "Real", but most just say "Power" and only differentiate Reactive and Apparent as being apart from that.

To add some possible confusion, when I worked for Siemens, it was referred to as "Active" power... In my German glossary it says "Wirkleistung", which translates back to Active Power, but also shows as Effective Power and Real Power! But then if you break the word apart, Leistung is Power, and Wirk is Work, so it really is "Work Power". So even they can't agree...

Bottom line, there is no difference between True Power and Real Power, or Active Power, or Effective Power, or Work Power or even just Power. It's all just semantics.

​

 
Status
Not open for further replies.
Top