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Tech Talk Voltage Transients
To most people, power quality is a mystery unless it is
a power outage or lightning strikes.
Studies show these events, while easy to
identify,
have the lowest potential of
any power quality problems you will encounter.
The highest number of power quality problems are
subtle low voltage transients that require test
equipment to identify their
existence
and over all frequency because often they are
intermittent.
The
repetition of malfunctions will require an examination
by a technical expert who can be challenged by the
intermittent nature of the problem.
Meanwhile, the user can begin to question a
product’s reliability (bad software or hardware?), the
technical ability of the “expert”, or the company that
manufactures or sells the system.
Power quality problems arise when system incompatibility
occurs between the AC power and the equipment. Either
the quality of the AC distribution system or the AC
voltage can contribute to power quality problems.
In each case, the solution is different.
In order to find the right solution, it is
important to diagnose the problem correctly.
According to the NEMA Surge Protection Institute,
voltage transients can be disruptive, dissipative, or
destructive to electronics.
Disruptive events, such as low voltage transients
simply cause
electronics to
lose their
performance reliability and can cause a computer
to lock up or other products to create error codes.
The importance of identifying disruptive events
is that they could
have high enough voltage levels to be
dissipative which means degradation of components
that can lead to equipment failure at some point.
Once voltage transients are identified, the next
challenge is to find the proper technology to mitigate
the problem.
As in any product, the effectiveness of a power
quality solutions can range from very little impact to
highly effective.
The next step is to weigh the balance of cost to
performance.
To protect systems from voltage transients, one needs to
protect against not only high voltage events such
as lightning
but also low voltage events which are most
commonly generated inside a facility from equipment
operating on internal circuits.
The
diagram below shows the results of mitigating high and
low voltage events.
IEEE ( Institute of Electrical and Electronics
Engineers) has designed numerous power quality tests
which are part of the standards in the power quality
industry. Illustration “A” shows the let through voltage
when high voltage is applied to the input of a computer
grade filter.
Let through voltage is what passes through a
power protection device to the equipment it is
protecting. The lower the voltage and the shorter the
duration - the better the protection.
There are many “surge protection devices” in the market
that are effective at reducing high voltage surges but
are not designed to effectively mitigate lower level
voltage transients.
In 1986 at their 5th annual
conference, the semi-conductor industry defined computer
grade filtering which is a critical level of protection
and allows electronics to operate as intended.
Computer grade filtering reduces voltage
transients to less than 10 volts on the line (normal
mode) and less than 0.5 volts neutral to ground (common
mode). This
is demonstrated by reducing surges (Illustration “A”) to
the computer grade level and reducing low level voltage
spike as seen on the sine wave (Illustration “B”).
Electronics will operate as intended if these
power events, which are over 80% of power quality
problems, are mitigated.
Illustrations A & B demonstrate how effective Smart
Power Systems patented transformer based filter
technology is at eliminating both high and low level
voltage transients.
Newer TBF Technology Yields Lower Cost -
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