Computer Power Supply/ups Compatibility

[PattayaDavid]

Hi all,

I only recently have built a Desktop PC, my first desktop model in a long time as I've always preferred notebook models for their portability. As anyone living in Pattaya knows, we do have our share of power outages. It wasn't a problem when I was using my notebook computer since it had a built-in battery backup, but with a desktop model, it's certainly a different story. I did however purchase an Uninterrupted Power Supply (UPS) for backup purposes for use during these outages. I purchased a Powercom IMD-1500AP model delivering 1500 VA, 900W, plenty big enough to power my computer and peripherals during a power outage allowing me to close programs and shutdown my computer.

I was looking through the manuals that came with my computer components when I ran across an interesting item that has now caused my concern. I have an Enermax Liberty 620W power supply in my computer. The manual states, use only Pure Sinewave Uninterrupted Power Supply units with this power supply. Pure Sinewave is the same type of current provided to our homes by the local electric company. Simulated Sinewave UPS units may damage the power supply unit. After further research on the internet, it seems like the Active PFC circuits found on most, if not all, better quality power supplies may be damaged by the current processed through the Simulated Sinewave UPS units. Browsing the internet, I couldn't find any quality power supplies, especially those supplying 500W or more that used passive PFC circuitry instead of the better regulating capable Active PFC.

My Powercom Imperial Series UPS model, unfortunately, uses Simulated Sinewave Technology. Even though I found the unit to be relatively expensive, 10,500 baht, from what I have gathered on the internet, a Pure Sinewave UPS model is substantially more expensive if you can even find one here in Thailand. I did find 2 models of interest while browsing the internet, the Powercom Smart King series, line interactive design and the slightly more expensive Powercom Vanguard series, true online design of UPS.

Sorry for all the lead up to my actual questions, but I thought it useful. First, have any of you, past or present, used a Simulated Sinewave UPS in conjunction with a computer power supply using Active PFC circuits? If so, have you experience any problems, loud noises etc. from your UPS or computer during a power outage? Does anyone know where I can purchase a Pure Sinewave UPS unit such as those I have mentioned in 1250VA or 1500VA capacity? How much would it cost me?

I would prefer to continue using my present UPS unit, but I am greatly concerned that it may damage my computer power supply during a power outage which I have yet to experience during my two weeks of ownership thus far. I would like to hear your thoughts concerning my problem.

Thanks,

Pattaya David

[paulfr]

I really doubt that this a problem to worry about very much.

I would hook it up and see if any problems develop.

These warnings are often more the legal department fears rather than engineering reality.

I am an electronics engineer who designs these things altho I never worked for an UPS company.

Most PS's have an inductive low pass filter on the input that would eliminate the problem components of the UPS output.

If yours does not, then one alternative is to get a PS with such a filter. [LC filter]

If you filter the UPS output, that also should eliminate any high frequencies. You can do this by getting a one to one transformer and putting it between the UPS and the PS. The inductance of the primary alone should wipe out any harmful HF.

Finally, even in the worst case that harmonics of the Simulated UPS hurt/damage the power supply, you can get a new one for some 2000 baht and make sure it doesn not have the active circuit causing the concern.

Let us know how it goes.

[Tywais]

I would prefer to continue using my present UPS unit, but I am greatly concerned that it may damage my computer power supply during a power outage which I have yet to experience during my two weeks of ownership thus far. I would like to hear your thoughts concerning my problem.

As paulfr mentions, it's unlikely to be an issue. However, if you are overly concerned, replace the PC power supply with a compliant one rather then the UPS - much cheaper solution.

[Guest Reimar]

You should also keep in mind that you'll need to have a proper Power Grounding for the UPS to work correctly. If your UPS came with Software and a special Data cable, I strongly suggest that you connects the Data cable from the UPS to the computer and install the software.

I mainly use Nova 1100 from MGE (french company) with Data cable connection, software installation and Grounding and have never any problems with actice or simulated PFC's but the only failure was with an Nova 1100 connected to an computer with Enermax 550 Watts PS (active PFC) but not any grounding, that PS was down within 1 week!