UPS and Power Consumption
 

My hands itchy liao.

Who needs a good backup power supply? I hope to DIY so need someone to sponsor this project. ;)

Diy Ups
 

Very x lei. But it's cheaper than buying one unit...

Computer UPS? they are nowhere near what I intend to do. The battery I intend to use will be in the range of 270Ah.

Bro, you in EE ah? Always wanted to know this :

In your eg. of a 270Ah battery at say, 12V, that's 3240Wh, right? Does this mean that it can supply an 80W pump power for about 40 hours? Or is that over-simplifying things, ignoring power loss, etc?

if the power convertion and pump efficiency is 100% then yr calculation is correct. However .. there are some points you may want to know.

Its not theoritically correct to use 3240Wh, its 3240VA (volt amp). If our equipment is purely resistive in nature .. then voltage X ampere = wattage. However magnetic pumps are inductive so they draw more ampere than what they actually need.

Look at the power triangle, true power (watts) + reactive power (VAR -Volt Amp Reactive) = apparent power (VA - Volt Amp). (Pythagoras Theorem applies here, (watts)2 + (VAR)2 = (VA)2 )

What we measured with our ampmeters are actually apparent power (VA), a combination of true and reactive power. We can also calculate the power factor by using true power divided by apparent power ( Watt/VA )

In our 230V household, we are not charged for usage of reactive power. So using electrical appliances with poor power factor will not incurr additional costs but it will draw alot more amperes due to their inductive nature. (Those so called energy saver by correcting power factor will NOT save you much money as we are not charged for reactive power!!)

Okay ... lets go back on track. You know why UPS are rated by VA and not wattage? Its because the internal battery will have to provide the reactive power while our 230V socket provide them FREE.

So if you got a 80watts pump with a power factor of 0.7

80/0.7 = 114.3VA

So yr pump is drawing 114.3VA apparent power instead of 80W true power. Do the necessary calculations and you can get the estimated runtime of the battery.

Another thing is the power inverter .. they are not 100% efficient so they may lose power by 10% or more by converting 12V to 230V. You will also need to factor this in.

Btw I'm not in EE, I'm in quality engineering .. a rojak engineering course.

you speaking english??
how come i dont understand a single thing??? :p :p :p

you will understand if you study simple AC power circuits :p

In a nutshell, take the ampere measurement of the pump and multiply by 230V, you will get the apparent power (VA)

UPS VA / Pump VA = run time (hrs)

e.g UPS - 1000VA / Pump - 100VA = 10hrs runtime

agree with you, i do not understand too....

Anyway WM just call me to tell me more on this project k.

Ming

Backup Power
 

Wah, you use all the deep deep stuff how to understand. You make one lei, than i can make a cheong version of yours....ke ke ke :p :p

lol nitro dont jump quee ! LOL i make 1st ,.. But what is he making ? LOL