Re: Surge Protectors

These buzz words - modified sine wave - computer grade - are how
color glossies sell inferior products to the naive. Numerical specs
are essential. For example, how clean is that UPS output? Is it clean
enough to operate small electric motors? 'Modified square wave'
suggests OK? Number that many plug-in manufacturers make difficult to
obtain - such as THD. Computer grade UPSes will output maybe 20% THD
- potentially destructive to small electric motors. Square wave or
stepped - its still 'dirty' electricity. A UPS best only for
computers: computer grade. If they don't define the term, then naive
would assume 'computer grade' as a cleanest output. Myths promoted
because numbers are not provided and understood. Clean UPS output
would be about 3%. On the oscilloscope, that low THD number would
actually look like a sine wave.

Why do bigger name UPSes sell UPSes with such dirty output
electricity? They are selling on price which is also why your car
battery can survive almost ten years - but a UPS battery typically
fails in three.

Sine wave output? Well technically yes. Square wave and stepped
wave is a sum sine wave at many frequencies. Those higher frequency
sine waves within a square wave are what would stress - potentially
damage - a small motor. So they did not lie, did they? 'Sine wave'
is to spin half truths on color glossies so that the naive will assume
and then promote a myth. 'Computer grade' does not mean cleanest.
'Computer grade' means a dirtiest output.

One factor not well understood is how low AC voltage can be.
Computer must power up and work just fine, as even demanded in Intel
specs for power supplies. When voltage is so low that incandescent
bulbs are at 40% intensity, still, every computer must both startup and
work just fine. How often does AC power drop that low? How often do
incandescent bulbs glow that dim? Well some cut costs on a clone
computer power supply, then require a $100 UPS to fix what should have
been inside a $30 more power supply. Many clone computers are
assembled using 'cost control' engineering which is why a UPS is then
hyped as necessary.

Above is a solution for blackouts and extreme brownouts - made better
if UPS informs and shuts down the computer. Noise and harmonics (third
and fourth power problem) are made irrelevant by computer's power
supply. Computer power supplies already contain any protection
effective on its power cord. Protection that assumes destructive
transients (fifth power problem) are earthed at building service
entrance - a 'whole house' protection system. If not installed, then
destructive transients can overwhelm protection already inside the
computer.

'Whole house' protectors are so effective and so inexpensive that a
telco installs one on every subscriber interface ... for free. Cable
TV does not even need a protector - cable must be connected by a wire
'less than 10 feet' to earth ground. Earth ground is the protection.
Telco 'whole house' protector is also only as effective as quality of
that earthing. The one incoming utility that requires homeowner action
(for Mac protection) is AC electric. Homeowner must provide an AC
electric 'whole house' protector (from Lowes, Home Depot, or electrical
supply houses) AND homeowner's earthing must both meet and exceed post
1990 NEC (National Electrical Code) earthing requirements.

Earthing - service entrance protection - solves this last power
problem (surges) so that destrutive transients do not overwhelm
protection already inside Macs. Earthing is also what ineffective
protectors avoid discussing.

Five power problems and five solutions, from a computer's
perspective.

Howard S Shubs wrote:
In article <1148400132.287631.187370@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
...
Your definition of "computer-grade" conflicts with how I'd define it,
but okay.

A 200 volts square wave - called a modified sine wave - ...

Some are squarish, sure. Others are stepped.
...

Okay, that's a new one to me. I just looked up the numbers for *my*
unit, a Best 610. It says Less than 4% THD at full linear load; less
than 7% THD at full non-linear load. What does this mean, please?

.

Relevant Pages

  • Re: power supply effects on Hard Drive?
    ... > I suppose that depends on what you consider "computer grade." ... >> then power strip also provides no effective protection. ... >> That same protection is also called 'whole house' protection. ... >> One final point - this UPS is called computer grade. ...
    (comp.sys.ibm.pc.hardware.storage)
  • Re: power supply effects on Hard Drive?
    ... a power strip protector located adjacent to the ... Effective transient protection also costs less money. ... does not have properly earthed 'whole house' protectors. ... that UPS is outputting a sine wave ... ...
    (comp.sys.ibm.pc.hardware.storage)
  • Re: Design Suggestion Requested
    ... But the Ritec RAM 10000 does synthesize a sine wave. ... While the spec may say 50ohms that usually means you should not load it with anything less at high power levels to avoid blowing the final stage transistors. ... The scientist wants the frequency to be adjustable to between 200kHz and 500kHz in single cycle pulses that pulse at rate of between 50Hz and 100Hz. ... But with a typical output of a DSS being 0V to 5V, and assuming the pulse transformer is 80% efficient, and unity gain for the buffer amp, I would need 500A into the pulse transformer. ...
    (sci.electronics.design)
  • Re: Simple Power Question
    ... The sine wave has amplitude 1 volt. ... the voltage specified is Vrms, which is Vp-p divided by 2*sqrt, the ... power calculations, which is what you are talking about here. ... integration by parts, but it is easier to just use the half-angle ...
    (sci.electronics.design)
  • Re: Battery backup: problem with my APC?
    ... when there was a split-second power outage. ... Despite the fact that my battery shows all 5 lights lit, ... And it aint even the continuous/online UPSs that mostly do produce TRUE sine wave output. ... A square wave is just a sine wave with large harmonics. ...
    (comp.sys.ibm.pc.hardware.storage)
Loading