Topband: Chassis Bonding

[Bill Wichers]

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
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband