Active and Passive pcf

[soulsaver_8229]

I want to get that Hiper 580 watt type R psu.........in the reviews it says it doesnt have an Active or Passive PCF on it............what are the bad/good points to this? I plan in the future to get a UPS, but not atm.......should that sway my desision on getting it?


soulsaver_8229

 

[[Spectre]]

http://www.vicr.com/documents/application_notes/an1_active-pfc.pdf
http://www.endpcnoise.com/cgi-bin/e/faqpfc.html
http://www.nasatech.com/Briefs/july04/ECC0704.html
http://powerelectronics.com/mag/power_power_supply_system/index.html

UPS Nonlinear Loads

Most end users are oblivious to the problems encountered when an online UPS interacts with nonlinear load, such as a switchmode power supply. Fig. 3, on page 42, illustrates the interface between an online UPS and a switchmode power supply. The switchmode supply within the host system consumes its current in high amplitude pulses, and as a result overloads the UPS, distorts its output and degrades in performance. This isn't the case if the SMPS has power factor correction (PFC); and in the United States most SMPS don't have PFC.

Repeated measurements under practical conditions show that in non-PFC SMPS, the current peak to rms ratio reaches a crest factor in the range of 2.5 to 3.5. This high crest factor imposes a difficult load for the UPS.

Manufacturers specify UPS capacity in volt-amperes, and set the UPS current limit with resistive loading. This affects the user in two ways: first, the actual power (in watts) that the online UPS can deliver is 75% to 80% of its VA rating. Second, the UPS cannot support a nonlinear load like a SMPS to full power capacity. In fact, it can support an SMPS only rated to 30% to 40% of its capacity. A 1kVA online UPS will only be suitable for backing up a system energized by a 300W to 400W (non-PFC) switchmode power supply. Attempts to draw higher power by the SMPS will severely distort the output of the UPS and may result in shutdown. Some UPSs support nonlinear loads to various degrees, but the above rule is safe to use as a guideline.

The whole idea of generating a high-purity sinewave within the UPS, and then rectifying it within the SMPS is wasteful. A UPS may be deployed to run non-electronic loads, such as lights or motors. However, this is a minor portion of the market for online UPS. Many applications back up computers and telecom devices, as well as instrumentation systems used for critical applications. In all of these applications, the immediate load for the UPS is the SMPS within the systems. Peak current and inrush current are associated with this load at startup. This current of 40A to 80A per SMPS will cause the UPS to shutdown due to overloading, or the UPS must transfer the load to utility to draw its inrush.

When using a UPS PFC is beneficial.

 

[soulsaver_8229]

very nice links, ty, now i understand what they are/do.......but will it hurt my system or cause anything bad to happen with out a UPS? and why is it by law to have a pcf in europe, but not here? or rather is it like that here but since thats a hong kong made psu out laws dont apply?


soulsaver_8229

 

[[Spectre]]

very nice links, ty, now i understand what they are/do.......but will it hurt my system or cause anything bad to happen with out a UPS?

Your system will be fine without it but most good high end units will have active PFC anyway.

and why is it by law to have a pcf in europe, but not here? or rather is it like that here but since thats a hong kong made psu out laws dont apply?


soulsaver_8229

From what I have heard (but this is not officially so I will double check it) is the Kyoto Accord. Active PFC is required in order to limit the effects of Total Harmonic Distortoin which affects the efficency of energy transfer. The worse the efficency of transfer the more power lost the more fuels needed to meet energy production etc. More fuel burnt....more greenhouse gas etc.