UPS

hi,
I wanted to know what kind of noise problem can one face in the power
output provided by UPS and how to get rid of them?
Reply to
vaishali
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The technical department of the manufacturer will discuss this with you, at length if you wish, /for a particular design make and model/.
The latter is the problem with your problem: there are many designs of UPS - from some which produce DC out, through square wave output, "modified" sine wave and "true" sine wave. Plus these are different designs on how they work, from continuous conversion through to "instant start and switch".
The noise can be due to the waveform chosen, the switching, the passthrough of noise from the supply, instability, Gaussian noise, etc.
You cannot easily get rid of noise totally and have useful power left- unless the power you want is noise power. "How to get rid of /some of/ it" can be from change to a different technology - eg using a DC output UPS or a true sine wave - both of which can be better than others, for entirely different reasons. Filtering could be used to get rid of it. Holding at constant temperature can help. Cooling can help.
Your one-line question could fill several books to answer and get many people their PhDs in the process..
Reply to
Palindr☻me
Just a quick answer from a practical standpoint. I work at a TV station with 100,000 W. UPS System.
The output of the inverter is not used directly as is the case in most smaller or portable UPS configurations. In a large permanent situation such as ours, the output goes through a regular sectioned iron-core isolation transformer rated for the full power of the load.
There is a limited, but effective filtering effect with this method as that any, fast, choppy discontinuities on the primary side are somewhat smoothed out on the secondary side. You might still have to deal with other effects such as harmonics, but those can be controlled to a certain degree with secondary filtering.
Beachcomber
Reply to
Beachcomber
Thanks for the reply. Can you tell me whether the surges, spikes and the transients that a UPS is supposed to compress are reduced upto what extent, and why are we unable to achieve a zero percent total harmonic distortion(THD), plus what are reasons of distortion of output supply in an SMPS(switch mode power supply).
Reply to
vaishali
Am I supposed to guess which UPS you have, or figure out an answer for all possible UPS?
Some UPS designs are extremely effective at reducing them - others less so.
Getting "zero" is not a realistic target.
The typical reason for "distortion" in the output of a switched mode power supply is that such a power supply uses a switch - eg has a non-continuous power transfer function.
-- Sue
Reply to
Palindr☻me
Hi, I need to have information about low-range, on-line UPS of 1.5, 3 or 5 KVA rating, they are produced by a comapany named APLAB.
vaishali.
Reply to
vaishali
although i just need a general information on UPS, basically the cause of distorted output in UPS generally.
Reply to
vaishali
They have an online contact form:
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The units you quote are specified as "Sinewave" out - but clearly aren't true sinusoid, not with a specified crest ration of 3:1.
They don't mention THD - but I would guess it is around the 2% mark of odd harmonics. Not bad. May be better on something approaching full load. It will probably have a bit of step noise. You are going to need a "true sinusoid" unit to find much better.
I assume it takes the input and converts it to DC at a suitable level for the battery/ies. Then uses a high frequncy inverter to take the battery supply up to levels of up to a few hundred volts that it uses as staircase points. Then converts that to 50Hz output. Most of the distortion/noise is going to come from the last stage.
The distortion is going to be because the output is more triangular than sine wave and has step points (eg more a staircase up and down) - although those hf components are probably pretty low rms values.
What more do you need to know?
Reply to
Palindr☻me
hi! no more futher questions. thanks a lot for your help!
Reply to
vaishali

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