Triplen harmonics, in most facilities, are caused primarily by lighting
ballasts and "electronic" (rectifier-input) power supplies. The newer switching
power supplies have a power factor controller in the first "stage" that acts
something like a current regulator preceding the actual switching power supply.
You can look up data sheets for these devices. The result is a .95 or better
power factor in most cases, and almost no generation of triplen harmonics on
the neutral. My understanding is that the EU requires power factor correction
in computer power supplies and since the manufacturers want to have one power
supply to use globally ("100 - 250 volts, 50/60 Hz", we've all seen this :-),
they just build to the most stringent standard and keep their volume costs down
with the single part.
The result of the corrected power supplies in datacenters is that we don't need
to use K-rated transformers (rated for high harmonic content) anymore which
saves a *lot* of money. I have found almost all of the "commercial" equipment
(network gear, routers, rack-mount servers) incorporate PFC. Many, but not yet
all, of the desktop computer power supplies are also going this route.
Newer electronic ballasts are also incorporating PFC. It's all part of an
effort to keep electrical costs down. It makes a difference in large
facilities, especially when you consider the long lifetime of most of the
commercial equipment involved.
-Bill
> > Triplen harmonics are also becoming less of an issue as many electronic
> loads now incorporate power factor correction.
>
> Interesting. Virtually all electronic equipment are "non-linear" loads
> -- they are the power supplies in that equipment, which virtually all include
> a
> rectifier and capacitor-input filter.
>
> 73, Jim K9YC
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