Can a modified sine wave UPS shorten a PSU's lifespan?

[Buck Naked]

Enlighten me.

 

[wanderer27]

If you're talking about what I'm thinking about, then no, it should actually be better.

Basically if I'm on the same track here, the modified Sine would actually be cleaning up the line power. There's a lot of noise/spikes on the power we get (motors, switches flipped, etc.). Some devices can actually change the Phase a little, so if we're talking about the same thing, the Sine UPS should actually be able to re-phase the signal - thus cleaning things up.

 

[pkme2]

I agree too. Anything helps.

 

[Jeff7]

Originally posted by: wanderer27
If you're talking about what I'm thinking about, then no, it should actually be better.

Basically if I'm on the same track here, the modified Sine would actually be cleaning up the line power. There's a lot of noise/spikes on the power we get (motors, switches flipped, etc.). Some devices can actually change the Phase a little, so if we're talking about the same thing, the Sine UPS should actually be able to re-phase the signal - thus cleaning things up.

Not sure if you are thinking of the right thing.
This is sine vs modified sine.
(Edit: Appears this is not accurate. This is a square wave vs sine wave. Thanks, Ms Dawn.)

A smooth sine wave is what you should get out of the wall socket. Modified is what most inverters will put out, simply because it's easier and cheaper to do.

I think a power supply should be alright with modified sine wave, because all it's going to do anyway is take AC input and turn it into reasonably stable DC output. But then, I don't know this for sure.

Things like electric motors might not like the rougher AC input, and either might not spin, or they could overheat. Imagine going to the beach, and instead of gentle waves, you'd just get walls of water smacking into you instead.

 

[Buck Naked]

Interesting...
I was under the impression that it was to save money.

 

[Bob Anderson]

To the pollster:

If you mean can a UPS on battery power and thus converting output voltage to AC, result in something less than a pure sinewave, and something more like a jagged or square wave, then the answer is yes for typical consumer UPS's. But PSU's have a lot of tolerance for noisy, dirty AC. They have to. Besides shoddy workmanship and poor parts, the most likely cause of PSU failure is heat and too much current draw. Failure from dirty mains AC supply would be rare.

High-end UPS's, sometimes called 'dual conversion' or 'line interactive' types, regenerate the battery output to new AC power, not just inverting the DC to AC. This produces a noiseless, perfect sine wave. The whole point of this is to extend the life of sensitive electronics. All medical- grade UPS's work that way.

-Bob

 

[wanderer27]

Originally posted by: Jeff7

Originally posted by: wanderer27
If you're talking about what I'm thinking about, then no, it should actually be better.

Basically if I'm on the same track here, the modified Sine would actually be cleaning up the line power. There's a lot of noise/spikes on the power we get (motors, switches flipped, etc.). Some devices can actually change the Phase a little, so if we're talking about the same thing, the Sine UPS should actually be able to re-phase the signal - thus cleaning things up.

Not sure if you are thinking of the right thing.
This is sine vs modified sine.

A smooth sine wave is what you should get out of the wall socket. Modified is what most inverters will put out, simply because it's easier and cheaper to do.

I think a power supply should be alright with modified sine wave, because all it's going to do anyway is take AC input and turn it into reasonably stable DC output. But then, I don't know this for sure.

Things like electric motors might not like the rougher AC input, and either might not spin, or they could overheat. Imagine going to the beach, and instead of gentle waves, you'd just get walls of water smacking into you instead.

Okay, that's not exactly what I was thinking about then. That's more of a Square wave than a Sine, though you are still getting + and - signals.

In this case, it shouldn't really matter. The PSU is just going to take these waves and run them through a Rectifier bridge and filter the output for smooth DC.

Looking at these waves, I have to wonder if the PSU will actually be able to pull as much power though. With a Sine wave you have a continously variable voltage signal that gets coupled through a Transformer (induction) to the Rectifier circuits. The squareness of these waves are more like an on/off, so the inductance (magnet wave) would be much shorter and thus less power would be available to convert to DC.

 

[Rubycon]

That picture is sine vs. square not modified sine. Stepped approximation to sine is closer to pure sine than square wave. Square wave should only be used in an emergency and when the driven device is capable of said operation.

 

[raincityboy]

Originally posted by: Bob Anderson
the most likely cause of PSU failure is heat and too much current draw. Failure from dirty mains AC supply would be rare.

Could a dirty AC line cause the PSU to heat up more then normal?

 

[Seekermeister]

Originally posted by: Jeff7
I think a power supply should be alright with modified sine wave, because all it's going to do anyway is take AC input and turn it into reasonably stable DC output. But then, I don't know this for sure.

Of course, the output from the UPS is AC, not DC. But you were probably referring to the internal output to the battery.

EDIT: There were a couple of comments by others, about rectifying current to AC, but that is done by inverters. Rectifiers produce DC. Apparently UPS has both...a rectifier to produce battery current, and an inverter to produce output current.

 

[wanderer27]

Originally posted by: raincityboy

Originally posted by: Bob Anderson
the most likely cause of PSU failure is heat and too much current draw. Failure from dirty mains AC supply would be rare.

Could a dirty AC line cause the PSU to heat up more then normal?

I would more expect it to be a "dirty" (dust) PSU than dirty AC, but if you're getting a lot of spikes (high voltage) or brown-out (low voltage) type signals, then this could cause your PSU to work a bit harder and hotter.

I wouldn't think it would be dramatic unless your lines are really bad though.

 

[Buck Naked]

Originally posted by: Seekermeister

Originally posted by: Jeff7
I think a power supply should be alright with modified sine wave, because all it's going to do anyway is take AC input and turn it into reasonably stable DC output. But then, I don't know this for sure.

Of course, the output from the UPS is AC, not DC. But you were probably referring to the internal output to the battery.

I thought he was referring to a PSU taking in AC, and outputting DC

 

[Bob Anderson]

Originally posted by: raincityboy

Originally posted by: Bob Anderson
the most likely cause of PSU failure is heat and too much current draw. Failure from dirty mains AC supply would be rare.

Could a dirty AC line cause the PSU to heat up more then normal?

I don't know. Never heard of that.

-Bob

 

[wanderer27]

Originally posted by: Buck Naked

Originally posted by: Seekermeister

Originally posted by: Jeff7
I think a power supply should be alright with modified sine wave, because all it's going to do anyway is take AC input and turn it into reasonably stable DC output. But then, I don't know this for sure.

Of course, the output from the UPS is AC, not DC. But you were probably referring to the internal output to the battery.

I thought he was referring to a PSU taking in AC, and outputting DC

Yes, the PSU is taking in AC and outputting DC for the Computer.

The UPS also rectifies power for charging the internal UPS Battery though.

 

[Buck Naked]

Originally posted by: wanderer27

Originally posted by: raincityboy

Originally posted by: Bob Anderson
the most likely cause of PSU failure is heat and too much current draw. Failure from dirty mains AC supply would be rare.

Could a dirty AC line cause the PSU to heat up more then normal?

I would more expect it to be a "dirty" (dust) PSU than dirty AC, but if you're getting a lot of spikes (high voltage) or brown-out (low voltage) type signals, then this could cause your PSU to work a bit harder and hotter.

I wouldn't think it would be dramatic unless your lines are really bad though.

My reason for asking is that my parents have been using a UPS for about 5 years, and in that time the PC hooked up to it has gone through 2 PSU's. Also 1 LCD monitor that was hooked to it died after about 3 years.
There are 2 other PCs in their house, and neither of those has had 1 problem.

I don't know what brand or model of PSUs that were used...

I am just wondering if this might be causing a problem or if they just have bad luck with that PC.

 

[wanderer27]

I would initially suspect Ligthning is a case like this. I lost a Computer that was on a UPS and wasn't even turned on this way

Do all the Computers have a phone line (internet) hooked up ? If only the one with the problem does, then that's likely the problem.

 

[Jeff7]

Originally posted by: MS Dawn
That picture is sine vs. square not modified sine. Stepped approximation to sine is closer to pure sine than square wave. Square wave should only be used in an emergency and when the driven device is capable of said operation.

Ok, so would the modified sine wave just have one step in it, instead of an immediate jump to the full voltage? If not, how many jumps must it have to qualify as modified sine?

I recall reading about "true" sine wave output inverters, that they still put out square waves, but that they just have a lot more steps, so they more closely approximate a true sine wave, enough so to be called sine wave inverters.

Originally posted by: Seekermeister

Originally posted by: Jeff7
I think a power supply should be alright with modified sine wave, because all it's going to do anyway is take AC input and turn it into reasonably stable DC output. But then, I don't know this for sure.

Of course, the output from the UPS is AC, not DC. But you were probably referring to the internal output to the battery.

EDIT: There were a couple of comments by others, about rectifying current to AC, but that is done by inverters. Rectifiers produce DC. Apparently UPS has both...a rectifier to produce battery current, and an inverter to produce output current.

I was actually referring to the computer's power supply, guess I didn't make that quite clear enough.


So the question still seems to remain: Does a continuous supply modified sine-wave AC input cause damage or undue stress to computer power supply? How much depends on the power supply itself? Some power supplies have a pretty wide input range, as well as some input filtering, others don't.

 

[Bob Anderson]

Originally posted by: Seekermeister

EDIT: There were a couple of comments by others, about rectifying current to AC, but that is done by inverters. Rectifiers produce DC. Apparently UPS has both...a rectifier to produce battery current, and an inverter to produce output current.

Thanks, Seekermeister. You are right about the term "inverting" and I edited my post.

-Bob

 

[Rubycon]

Originally posted by: Jeff7

Ok, so would the modified sine wave just have one step in it, instead of an immediate jump to the full voltage? If not, how many jumps must it have to qualify as modified sine?

I recall reading about "true" sine wave output inverters, that they still put out square waves, but that they just have a lot more steps, so they more closely approximate a true sine wave, enough so to be called sine wave inverters.

Text

A true sine wave inverter produces a sine wave at 50/60Hz and will look identical to utility grade mains - providing it of good design. A square wave inverter can not remotely be called a sine wave, they're completely different things. If a "sine wave" inverter produces a square wave on a 'scope, it is malfunctioning!

 

[Seekermeister]

Originally posted by: wanderer27
I would initially suspect Ligthning is a case like this. I lost a Computer that was on a UPS and wasn't even turned on this way

Do all the Computers have a phone line (internet) hooked up ? If only the one with the problem does, then that's likely the problem.

APC has a $150,000 insurance policy available, if any hardware damage occurs while using their product. I do not know about other UPSs, but mine does have telephone connectors, but I think that they are only for surge protection. But then, I recall reading something in their magazine about it protecting against loss of telephone service, so I may well be wrong.

 

[Jeff7]

Originally posted by: Buck Naked
My reason for asking is that my parents have been using a UPS for about 5 years, and in that time the PC hooked up to it has gone through 2 PSU's. Also 1 LCD monitor that was hooked to it died after about 3 years.
There are 2 other PCs in their house, and neither of those has had 1 problem.

I don't know what brand or model of PSUs that were used...

I am just wondering if this might be causing a problem or if they just have bad luck with that PC.

The UPSes will only output this modified sine wave when they're running off of the battery. Otherwise, the current will only be passing through the surge protection circuitry of the UPS - it'd be no different than if you just had a surge protector.

Most consumer-level UPSes are really SPSes - Standby power supplies. They switch on only when they detect that the mains have fallen below a certain level. This can introduce a slight delay. Newer units have faster switching times, but the older ones, like around 1997 (when I bought my first UPS) took longer. My monitor would blink when the power would go out - that was the time it took for the relay to kick in. With my new UPS, There's not so much as a jump in the image, at least not that I can see.

A true UPS is set up so that the attached equipment is always running off of the inverter, which is attached to the battery. This way there is no delay whatsoever to the attached equipment. These are expensive though. I imagine the part that makes them expensive is the hefty 12VDC power supply they need to not only keep the battery charged without overcharging it, but also be able to provide enough current to run the PC continuously without overheating. That, and being higher end equipment, they might also use a sine wave inverter, making them even more expensive.