PC Protection During Thunderstorm Season

[westom]

 

However, as I also mentioned above, due to the EU regulations, devices themselves do have some level of protection built into the devices themselves, so are more fault tolerant then they would be otherwise.

 

 

 Some appliances make anomalies such as power factor and harmonics irrelevant - as all agree.  Others do not.  A UPS in battery backup mode can have excessive harmonics.  Therefore UPS manufacturers quietly recommend a UPS not be used on motorized appliances. Anomaly made irrelevant by one appliance is problematic for another.  Apparently you did not know harmonics and power factor are relevant to some appliances.

 

BTW, EU standards define power factor generated by some appliances.  It does not address how power factor can be problematic to others.

 

 You asked a question relevant to all - not just you.  What is the risk?   All appliances are already robust as required by EU, UL, ANSI, IEC, Bellcore, CSA, FCC and ISO and other standards.   Unfortunately others assume a UPS will cure all anomalies.  'Dirtiest' power an appliance might see comes from a UPS in battery backup mode.  Cleanest power is when that UPS connects that appliance directly to AC mains.  Harmonics created by a UPS can be problematic to some appliances. A short list of anomalies were provided as examples.

 

A UPS is protection for unsaved data.  Typical UPS does not include 'cleaning' features you have assumed (ie frequency variation).  Some 'dirtiest' power can be created by a UPS in battery backup mode.   So how often do anomalies become harmful?  Which appliance really is at risk?  Computer, smoke detector, or furnace?  Standards and superior appliance design make most anomalies irrelevant.   As you demonstrate by example, a typical UPS does nothing useful for so many.  Because it only addresses one harmful anomaly - loss of unsaved data. And because appliances are designed to be robust.

 

OP's battery backup does not address other anomalies that concerned the OP. Manufacturer spec numbers say so. Some UPS create 'dirtier' power.  And still, so many recommend a UPS to do what it cannot and does not do.  To cure anomalies that, as you demonstrate, are not problematic.

[HawkMan]

 Some appliances make anomalies such as power factor and harmonics irrelevant - as all agree.  Others do not.  A UPS in battery backup mode can have excessive harmonics.  Therefore UPS manufacturers quietly recommend a UPS not be used on motorized appliances. Anomaly made irrelevant by one appliance is problematic for another.  Apparently you did not know harmonics and power factor are relevant to some appliances.

 

 

Huh, I always thought and heard you're not supposed to use UPS on motorized AC equipment because the UPS generally created square curves, not nice clean sinus curves that AC motors rely on. 

[snaphat (Myles Landwehr) Member]

Huh, I always thought and heard you're not supposed to use UPS on motorized AC equipment because the UPS generally created square curves, not nice clean sinus curves that AC motors rely on. 

A stepped sinusoidal signal or even a square wave itself is really just a set of combined harmonics. But, basically, it's really just saying the same thing differently so you are correct. It isn't like this is hidden and the UPS manufacturers are trying to pull the wool over our eyes anyway.  :)

 

See:

http://en.wikipedia.org/wiki/File:SquareWave.gif -- example of a square wave approximation using harmonics

http://en.wikipedia.org/wiki/Harmonics_(electrical_power)#Current_harmonics -- note the talk about the fourier series 

http://en.wikipedia.org/wiki/Harmonic

 

EDIT: Also, I should note, that in reality that no signal is ever really perfectly 'square' in either a square wave or an approximated stepped sinusoidal. You just see ideal representations in literature. If you zoomed in on the signals, they would have the banding effects shown in the example square wave along the edges and have a rise and fall times.

[westom]

A stepped sinusoidal signal or even a square wave itself is really just a set of combined harmonics. ...

 

See:

http://en.wikipedia.org/wiki/File:SquareWave.gif -- example of a square wave approximation using harmonics

http://en.wikipedia.org/wiki/Harmonics_(electrical_power)#Current_harmonics -- note the talk about the fourier series 

 

First wikipedia citation demonstrates what we all were (should have been) taught in high school mathematics.  A square wave (like any repeating wave) is nothing more than a sum of pure sine waves.

 

A UPS manufacturer may invent 'subjective' claims to manipulate the naive.  As long as numbers are missing, then any 'dirtiest' UPS output is called a "pure sine wave" output.  Advertising claims, intended to lie or deceive, are perfectly legal and correct without specification numbers.  Another example of why any claim without spec numbers should be considered bogus or suspect.

 

Second wikipedia citation defines an important number: %THD.  If a UPS manufacturer is being honest, then his specifications come with a %THD number or something equivalent.  Good luck finding %THD numbers on specs for APC or a similar UPS.  These products are recommended by many who would not even know what %THD means or measures. Keeping consumers naive or ignorant can increase sales.  Same subjective claims also promote a UPS for 'clean' power.

 

UPS is temporary and 'dirty' power so that unsaved data can be saved.  Due to superior protection in power supplies and other electronics, then a 'dirtiest' UPS is also ideal power for electronics.

 

Best protection at an appliance is usually and already inside that appliance. So that harmonics and transients cause no problem.  But you would never know that from subjective myths and bogus claims made to sell a UPS or power strip protector.  Honesty (be it appliances or even justifications for war) means each recommendation comes with perspective - numbers.

 

Numbers separate an informed recommendation from hearsay.