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| Comments
regarding power disturbances |
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Power
quality varies significantly from one area to another. Some countries
have very stable power grids while others are extremely short
on capacity.
Power disturbances are caused by the generation, distribution
and use of power; and lightning.
A power disturbance can be defined as unwanted excess energy that
is presented to the load.
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| Causes
of power disturbances |
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Power
disturbance originate both outside and inside customer facilities.
Load switching causes surges because of collapsing fields (-e
= l * di/dt).
Over loaded power distribution systems can cause significant voltage
variations between peak and off-peak hours.
Significant momentary load changes, such as heavy inrush currents
can cause severe voltage variations.
Black-outs can cause severe voltage surges both on loss and return
of power.
Circuit-breaker tripping and fuse blowing can cause severe surge
voltages.
Large ups and variable-speed drives can cause various surge voltages
inside buildings.
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| Results
of power disturbances |
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Sags
and under voltages can cause component overheating or destruction.
Surges and over voltages can cause component overheating, destruction
or can trigger other electronic components such as scrs.
Component overheating reduces the life and deteriorates the real
reliability as opposed to the estimated reliability based on steady-state
conditions of the product.
False triggering of other components can create nuisance alarm
tripping or, worse, can cause overheating or destruction of other
electronic components.
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| Problems
with current solutions |
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Common-mode
voltage disturbances can be amplified in non-tn-s ac distribution
systems.
Typical EMI filters are not well damped. This has a dramatic effect
on any voltage disturbances, resulting in oscillations inside
the emi filter under any transitional conditions. Severe voltage
surges may result from fly-back from saturated inductors looking
for a path to release energy.
Boost converters can be destroyed by surges causing increased
energy storage in input filter, the output capacitor (c) is charged
to an unsafe level depending on capacitance value and load levels
for the dc/dc converter connected to the output of the boost.
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