I'm not sure if this is the right place to post this, so if I should post somewhere else, someone please let me know.

I'm having a small disagreement with a co-worker. He says that there are situations where power factor can be greater than 1 (for ex. if you have a large capacitive load like a large unloaded UPS system). He also tells me that there are some high efficiency motors with 1+ power factors. How is this possible? I thought that power factor could never be more than 1. I also understand that PF is the cosine of the angle between the current and voltage, and therefore can't have a value greater than 1. So, as far as I can tell, I'm right. The math doesn't lie. But am I wrong?

I've asked this question to a couple of electricians who I thought would know the answer, and they all said they "think" it "might" be possible to have a PF slightly over 1. It seems there are a lot of trades people out there with a vague understanding of power factor...myself included.

Thanks.

 

http://en.wikipedia.org/wiki/Power_factor

I think you're right. It sounds suspiciously like over unity. If I understand the definition correctly it is the ratio of power sent vs. power used.

 

No.
It is a number between 0 and 1. It would be extremely difficult to get to either 0 (undesirable) or 1 (desirable), as the parasitics would always knock things a bit out of kilter.

http://www.allaboutcircuits.com/vol_2/chpt_11/3.html

http://en.wikipedia.org/wiki/Power_factor

 

Bill beat me to it But the three of us are in agreement.

 

Power factor can't be more than 1. See:

http://en.wikipedia.org/wiki/Power_factor

You'll notice that this meter:

http://www.laurels.com/phase.htm

measures from 1.000 to 0.000

It doesn't measure greater than 1.

 

The simple explanation is that since it is equal to the cosine of the phase angle from voltage to current it must lie in the range 0 to 1 if the phase angle is in the range [-90°,...,+90°]

 

When he talks of motors being 1+ I think he is thinking of service factor not power factor.

 

When he talks of motors being 1+ I think he is thinking of service factor not power factor.

Never heard of it. What is service factor?

 

Never heard of it. What is service factor?

Click here: http://www.engineeringtoolbox.com/service-factor-d_735.html

 

Thanks for the great responses. I had already read the wiki post, but still was unsure if maybe I was unaware of something. It all sounded like "snake oil" to me. I just started reading the e-book to further my knowledge. I have a basic understanding of electricity, but I would like to get more involved in electronics. It's good to know there's a place where I can go when I have a question, and people are willing to help without the usual forum hazing.

Thanks again.

 

Welcome to ACC! Now, tie this end of rope to your neck and throw this brick tied to the other end off of the building. And drink ten shots of Cuervo. Hazing is complete.

 

Click here: http://www.engineeringtoolbox.com/service-factor-d_735.html

Thanks for that. It is hard to imagine that was intended given the context of the original post. In that original post it was a clear expectation that there was some "magic" combination or arrangement of reactances that would lead to a powerfactor greater than 1. The service factor seems to have more to do with the ability to handle elevated temperatures as a result of overload conditions.

 

Exactly... The magic combo would be high capacitive load. (according to my co-worker). The way he thought it worked was that somehow inductive load pulled the power factor down, and capacitive load would therefore increase it. Therefore, if you have no inductive load, but you have a significant capacitive load... PF>1.

I didn't think this was how it worked.

Thanks again.

 

NB (Nota Bene) -- A large capacitive load would be produced by a very small capacitor at a very low frequency. If you consider the formula for capacitive reactance

Xc = (1 / 2∏fC)

Consider a 10 pf Capacitor at 0.001 Hz

(1 / 2∏(.001)(10 x 10^-12)) = 15.915 x 10^12 OHMS !!

Getting a circuit to have very low inductance, and thus a low inductive reactance is also a considerable challenge.