Re: Power issue follow-up question: UPS?

On Mar 14, 1:21 am, "Keith" <piotrNOSPAM1...@xxxxxxxxx> wrote:
...
But if we look at what happens when there is a power outage / power flicker
/ spike whatever you want to call it... The causes of those can be pretty
wild - drunk + car + power pole is pretty common, as is lightning. Or yer
local power company has a generator that drops off line, or someone hits an
emergency stop button in that big plant across town... In any event, the
load the power company sees suddenly changes, and the voltage may go wildly
out of control for a short duration as the equipment that regulates the line
voltage adjusts to the new load. The result is that there may be voltages
rising *well* above 'damage potential' for your equipment, or falling below
the minimum operating voltage... Or both. You can easily get spikes of
voltage whose duration can be in the sub-millisecond range but whose
amplitude is high enough to destroy almost *any* design. ...

Electronic industry standards defined massive voltage changes that
must never cause damage. For example, charts for voltages that are
too low contain this expression: "No Damage Region". 120 VAC power
that drops below 108 volts or 84 volts is the "No Damage Region". Low
voltages must never cause electronic appliance damage.

Same charts also define high voltages that 120 volt electronics must
withstand without damage: voltages up to 600 volts. This is industry
standard for all electronics. Some electronics (ie computers) must
withstand up to 1000 or 1800 volts without damage. Why do we install
one 'whole house' protector for about $1 per protected appliance (as
discussed by John O)? So that protection inside appliances is not
overwhelmed.

Current surges during power on also must not be destructive to
electronics. To make electronics even more robust, electronics
include a device called an inrush current limiter - as even installed
in 1950s TVs. Greatest risk is the sudden turn on in normal
operation. If grid power is being restored and voltages rise slowly -
then current is limited even more. This is also better for
electronics for the same reason why electronics contain an inrush
current limiter.

Of course the above does not apply to motorized appliances. Motors
do not like slowly rising voltages or more than 5% reduced
voltages. Some confuse what a motorized appliance does not like
with what an electronic appliance finds normal.

If voltage goes so high as to harm electronics, well, what might do
that? As noted previously, that UPS example exposed 120 volt
electronics to spikes as high as 270 volts. So a UPS can also damage
electronics? Again, view above numbers. Electronics that meet
industry standards should withstand 600 volt spikes without damage.
How do we limit those spikes so that internal appliance protection is
not overwhelmed? One 'whole house' protector. After all, when do we
most need those smoke detectors? When the grid is spiking above 600
volts. What protects everything including the amp and especially all
smoke detectors? One 'whole house' protector with proper earthing.

Does a UPS provide protection? Of course not. Those who
recommended a UPS for electronics protection cannot even provide
numbers. UPS manufacturer (ie APC) does not claim what some have
posted here. This post numerically defines each electrical threat.
A threat that may overwhelm internal appliance protection is mitigated
by one properly earthed 'whole house' protector. Expensive? Yes, a
'whole house' protector costs about $1 per protected appliance. But a
UPS that does not even claim to provide such protection costs maybe
$100 per appliance. Which is more expensive?

Of course, this assumes the appliance is properly designed according
to standards that even existed 35 years ago. Electronic appliances
should contain significant internal protection that makes must
electrical problems irrelevant.


John Bigboote asked about a voltage clipping problem. How many
watts are consumed by his amps? 1400 watts? If not that high, then
one AC electric receptacle must provide sufficient 120 VAC
electricity. Clipping would be an amp power supply that is failing.
UPS would not correct a defective power supply. Most UPSes cannot
even provide 1400 watts; cannot do what one AC electric receptacle
must provide. Again - the numbers.

Power supplies must provide voltages without clipping; even when AC
voltages go so low that incandescent bulbs dim to 40% intensity. Amp
supply must work when lamps dim; with no clipping. Making amp
voltages unaffected by AC line variations is a power supply's job.
Either amp voltages are fully in spec, or amp shuts down. If his amp
voltages are clipping, then the amp power supply is failing and the
defect is probably slowly getting worse.
.

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