Sensitivity settings on Back-UPS ES Models

[Anonymous user]

On the APC Knowledge Base you can find a document showing the voltage disturbances that can make a Smart-UPS transfer to battery power and what kind of voltage disturbance each level of sensitivity can detect. The document I'm talking about is this:

http://lam-en.apc.com/app/answers/detail/a_id/62/kw/Sensitivity/session/L3RpbWUvMTI4MTc1MzIxMS9zaWQv...

What I want to know is if the sensitivity setting for the Back-UPS line works the same way as on the Smart-UPS line. Does the Back-UPS line detects the same kind of voltage disturbance as the Smart-UPS line?

Thanks!

[voidstar_apc]

>
I asked this because the Smart-UPS line look for THD - Total Harmonic Distortion - and since it is a known subject that a stepped sinewaves contains a good amount of harmonic distortion, I was thinking it wouldn't be very clever for the Back-UPS line to look for harmonic distortion, unless the THD of a Back-UPS unit is lower than the level detected on the AC Sinewave prior to transferring to battery power.
>

For a single Back-UPS unit, the criteria for the AC line being good seems unrelated to the output waveform. Of course if you plug one Back-UPS into another, I'd expect them both to go on battery when AC is bad.

[Anonymous user]

My point is, if the Back-UPS transfers to battery because of detected harmonic distortion on the AC sinewave, it won't do any usefull work since the output wave of the Back-UPS models is full of harmonic distortion as well, I just don't know how much. For the Smart-UPS unit APC says the THD is lower than 5%, which is better than the AC sinewave of many facilities.

[voidstar_apc]

>
My point is, if the Back-UPS transfers to battery because of detected harmonic distortion on the AC sinewave, it won't do any usefull work since the output wave of the Back-UPS models is full of harmonic distortion as well, I just don't know how much. For the Smart-UPS unit APC says the THD is lower than 5%, which is better than the AC sinewave of many facilities.
>

Ah, I think I see what you're saying: If the purpose is to protect the attached devices from harmonic distortion, then transferring to battery and generating a psuedo-sinewave when such distortion is detected defeats the purpose.

I think the purpose is to detect power failures before the voltage dips too low. In the time domain, such disturbances are sudden deviations from a perfect sine wave. In the frequency domain, that shows up as harmonic distortion.

[Anonymous user · Accepted solution]

On the APC Knowledge Base you can find a document showing the voltage disturbances that can make a Smart-UPS transfer to battery power and what kind of voltage disturbance each level of sensitivity can detect. The document I'm talking about is this:

http://lam-en.apc.com/app/answers/detail/a_id/62/kw/Sensitivity/session/L3RpbWUvMTI4MTc1MzIxMS9zaWQv...

What I want to know is if the sensitivity setting for the Back-UPS line works the same way as on the Smart-UPS line. Does the Back-UPS line detects the same kind of voltage disturbance as the Smart-UPS line?

Thanks!