Power Factor for modern PC components?

[tinted]

So, a friend asked me to find UPS for his system. Rough worst case estimate of power usage for that system should be 500W, so with PF of 0.6(everyone likes this number) a UPS above 830 VA should be enough. But I want to understand this better.

His sys specs

• intel 13400
• 6750xt
• DDR 4 ram, 8GB x 2
• 1tb crucial p3
• corsair RM850e 
• 27" QHD 165hz monitor, have to ask for model number.
• dont remember motherboard model or make

so now my doubt is what are the power factor for each of those components. Main power consuming components are CPU, GPU and then monitor. So if we account for them it is enough right?

I asked google bard for PF values for CPU and GPU and it tells me that they should be 0.85 - 0.95 for intel CPU, Nvidia GPU and 0.8 - 0.9 for AMD cpu and gpu. Are these values correct and what about monitor PF.

 

Modern power supplies also comes with PFC( power factor correction circuits).so, Another question is since PSU have PFC circuits, does it even matter what the components PF values are since they are dealt with in PSU and all that matters is PSU efficiency? 

If not then should we first calculated total power for CPU, GPU and then multiply with PSU efficiency to get final system power? and why does UPS makers assume 0.6 as power factor, I mean they give rated power in Watts so low compared to rated power in VA.

 

APC UPS product link

 

[manikyath]

ignore the VA rating on UPSes, they all have a wattage rating as well, and your computer's power factor is good enough that the wattage rating is your limit, not the power factor.

 

EDIT: PS, i should also add, "power factor" is an AC power thing, the moment you're past the power supply none of it matters.

[tinted]

10 minutes ago, manikyath said:

ignore the VA rating on UPSes, they all have a wattage rating as well, and your computer's power factor is good enough that the wattage rating is your limit, not the power factor.

ya, but UPS link I sent you has wattage rating correctly at 0.6 percent of VA rating. And I think it is calculated safe wattage value with assumption being connected load PF to be 0.6, which I don't like since electronics now a days have better PF values. But ofcourse it is not bad thing since it would be overkill and overall better for the system. I just want to understand this better.

 

edit: yep, its AC thing, I forgot about that but that mean it should not matter if CPU and GPU have a PF value and also that Bard results could be better

[manikyath]

1 minute ago, tinted said:

ya, but UPS link I sent you has wattage rating correctly at 0.6 percent of VA rating. And I think it is calculated safe wattage value with assumption being connected load PF to be 0.6, which I don't like since electronics now a days have better PF values. But ofcourse it is not bad thing since it would be overkill and overall better for the system. I just want to understand this better.

nope, that's not how it works. it'll do 1400VA on a shyte power factor, or 865W on a good power factor.

 

in simple terms, the way it works is that all places current travels trough can handle 1400VA (volts times amps, if you're in 240v land that's 6A), but the bits that deliver the power can 'only' handle 865 watts (volts times amps, again if you're in 240v land that's 3.6A... or 36A from the battery, assuming it's a 24v battery.)

[tinted]

14 minutes ago, manikyath said:

nope, that's not how it works. it'll do 1400VA on a shyte power factor, or 865W on a good power factor.

 

in simple terms, the way it works is that all places current travels trough can handle 1400VA (volts times amps, if you're in 240v land that's 6A), but the bits that deliver the power can 'only' handle 865 watts (volts times amps, again if you're in 240v land that's 3.6A... or 36A from the battery, assuming it's a 24v battery.)

ok, It did not make full sense to me yet but what I understand from your second para is something like the wires can handle 6A but the electrical and electronic components that do the work can only do 3.6A. Regardless of whether what I understood is correct or not basically its UPS makers marketing bullshit. If not bullshit then is it something electrician use for calculating some other aspect?

Edit: I did know that VA rating is some BS but after trying to learn a little more I though maybe I understood it wrong but now I am thinking it is misleading marketing BS again.

 

But your first statement is little confusing, in theory it is usually W = VA x PF right but if what you say is true then in this case they are not related at all.

[Kilrah]

Basically any decent PC power supply has active PFC now, so it'll have a power factor close to 1. As mentioned the VA rating that's for some reason still the main spec on UPSes (obviously just to have bigger advertised numbers) is entirely meaningless, you should look at the W spec and only care about that being sufficient.

[tinted]

1 minute ago, Kilrah said:

Basically any decent PC power supply has active PFC now, so it'll have a power factor close to 1. As mentioned the VA rating that's for some reason still the main spec on UPSes (obviously just to have bigger advertised numbers) is entirely meaningless, you should look at the W spec and only care about that being sufficient.

hmm, I guess that VA number is just BS. I though maybe I could get away with smaller UPS but i guess not. 

[manikyath]

2 minutes ago, tinted said:

hmm, I guess that VA number is just BS. I though maybe I could get away with smaller UPS but i guess not. 

it's not BS.. if you're running 800 watts worth of AC motors off of your UPS.. but that's about as likely as a floating computer.

[tinted]

14 minutes ago, manikyath said:

it's not BS.. if you're running 800 watts worth of AC motors off of your UPS.. but that's about as likely as a floating computer.

So like you said before, it can do 1400VA (or roughly 800W) for bad components like AC motors but also very similar around 800W for components with good PF. My whole confusion is because I though those two numbers are related but they are not. Even though they can be converted into each other they are specifying different things which I will only understand when I understand the electrical subject related to this more

[manikyath]

1 hour ago, tinted said:

So like you said before, it can do 1400VA (or roughly 800W) for bad components like AC motors but also very similar around 800W for components with good PF. My whole confusion is because I though those two numbers are related but they are not. Even though they can be converted into each other they are specifying different things which I will only understand when I understand the electrical subject related to this more

the limit is "either" 865 watts, or 1400VA, whichever comes first (depending on power factor)

 

EDIT: see it as, for example, the load volume of a van could be 500kg *or* 1000 liters, whichever comes first. hauling steel the 500kg is reached first, hauling feathers the 1000 liters will be a problem first.