[
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2008, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]
64.65.92.138
In Reply to: RE: Let's reverse-engineer the PS Audio Noise Harvester posted by tomservo on June 03, 2008 at 15:23:08
Tom, thanks a ton for sharing a detailed explanation of the noise issue. I think your explanation may also cover why some people hear changes when they change power cords. As John Camille said in an article on induced noise, If you hear a change when you change power cords, your power supply needs work.
Also, your point about how much RFI we generate ourselves is a key issue IMHO. I worked on a case once where a high-rise power distribution bus failed due to harmonics on the AC line created by all of the SMPSs in the building. I'm talking about a 440 volt 3-phase busway that used 1/2 by 4 inch aluminum busses to carry the current required by the tenants in part of the building; apparently harmonic-related heating overloaded the busses to the point where arc-over actually vaporized a couple of feet of those aluminum bars. Here's an explanation of the problem:
Typical three-phase electrical distribution busways include a housing, an A-phase busbar, a B-phase busbar, a C-phase busbar and a neutral busbar, where all of the busbars have substantially the same cross-sectional area. Examples of these types of busways are found in U.S. Patent Nos. 5,151,043 and 3,391,378. Under conditions where a busway is providing electrical power to a substantially overall balanced linear load, the fundamental 60 Hz portion of the phase currents should cancel each other in the neutral busbar. However, where a busway is providing power to an overall load which has non-linear and unbalanced components, the electrical current in the neutral busway can exceed the phase currents. As a result, unacceptable heating of the neutral busbar may occur.
It is believed that non-linear loads (e.g. power supplies, motor drives, computers, printers, etc.) cause unacceptable electrical current levels in the neutral busbars of a three-phase system as a result of the harmonics introduced by the non-linear loads. (See, Fluke - In Tune With Power Harmonics, pp. 1-15, 1991.) More specifically, certain harmonics do not cancel, but are additive and increase the currents in the neutral busbar.
A bit off-point, I know, but still an indicator of how much junk is sent into the AC line by SMPSs.
Follow Ups:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2008, Audio Asylum, all rights reserved ]