The subject of reactive power is one of the more complex aspects of electrical
energy... and probably classifies as the most widely misunderstood, even by
master electricians.
It's also situations such as this that give reputable inverter manufacturers a
strong case of heartburn.
Just as there are customers who are fooled by the "power saving" devices that
are marketed in one form or another under the guise of "recycling 'wasted'
power", it's easy to make all kinds of claims/detractions as to benefits of a
particular inverter's use or operation.
For an inverter to generate "reactive" power would require shifting its output
current to lead or lag the voltage waveform on the grid to which it's connected.
For this to occur, the inverter would require a means of measuring the actual
power factor. Since inverters are not in line with the load (or shouldn't be
per the NEC), this simply isn't possible. Claims to the contrary are, as Bill
Brooks pointed out, "BS Meter" warnings.
Work is underway to develop inverters that, under utility company control, can
generate "leading or lagging" power to help actively offset power factor
conditions that exist within the grid proper, but not yet at individual sites.
(Also note the operative words "under utility company control".) These will,
in effect, become active versions of the capacitive banks installed by power
companies to correct power factor issues caused by known (and static)
inductance resulting from long runs of transmission lines.
Along with the topics of politics, religion, and others .. power factor has
long since been added to my "do not discuss in public" list. There are simply
too many who don't understand it, yet are self-convinced otherwise. Bill's
comments in his earlier post to this topic are spot on target....
Dan
Sr. Engineer
Exeltech
--- On Fri, 1/7/11, Jamie Johnson <jjohn...@spefl.com> wrote:
From: Jamie Johnson <jjohn...@spefl.com>
Subject: Re: [RE-wrenches] Xslent?
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Friday, January 7, 2011, 11:51 AM
Interesting website August, not sure if it uses a battery backup or simply
supplies/returns reactive power at night from normal inductive loads. In their
graph they list what items were running during the test and some of them are
inductive loads, if they are capturing the reactive power and returning it back
to the inductive load that may be how they are increasing their KVAh output at
sunrise and sunset? Most customers are only charged for KWh not KVAh though.
A 24 hour chart might help.
Also, not sure if it has a 1 year or 20 year warranty, both are listed on the
site.
They say that the output is 120vac and it can be hooked up to a 480v 3 phase
service, however, they fail to mention that you would need a customer supplied
transformer in order to make the connection.
It does not use capacitors which is probably a plus if you are mounting it
under a module.
And it would be nice to see a real world independent test of the product.
Maybe Enphase has something similar in the works that it could be compared to.
Jamie
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