Transcript TRANSFORMER ISOLATION AND OPTICAL ISOLATON SIGMA

SIGMA INSTITUTE
OF ENGINEERING
TRANSFORMER ISOLATION AND
OPTICAL ISOLATON
Submitted to,
Mr. Dinesh F. Rajput
(Lecturer,
E & C dept.)
Submitted By,
Hardik chhasatiya
(130500111003)
Lakshya shrungarpure
(130500111008)
Hiral rathod
(130500111022)
PPT INCLUDES...
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Transformer isolation
Operation of transformer isolation
Application of transformer isolation
Optical isolation
Operation of optical isolation
Application of optical isolation
TRANSFORMER ISOLATION
An
isolation
transformer
is
a transformer used to transfer electrical
power from a source of alternating
current (AC) power to some equipment or
device while isolating the powered device
from the power source, usually for safety
reasons. Isolation transformers provide
galvanic isolation and are used to protect
against electric shock, to suppress electrical
noise in sensitive devices, or to transfer
power between two circuits which must not
be connected. A transformer sold for
isolation is often built with special insulation
between primary and secondary, and is
specified to withstand a high voltage
between windings.
TRANSFORMER ISOLATION
Isolation transformers block transmission of the
DC component in signals from one circuit to the
other, but allow AC components in signals to
pass. Transformers that have a ratio of 1 to 1
between the primary and secondary windings
are often used to protect secondary circuits and
individuals from electrical shocks. Suitably
designed
isolation
transformers
block
interference caused by ground loops. Isolation
transformers with electrostatic shields are used
for power supplies for sensitive equipment
such as computers, medical devices, or
laboratory instruments.
OPERATION OF ISOLATION
TRANSFORMER
Isolation transformers are designed with attention to capacitive
coupling between the two windings. The capacitance between
primary and secondary windings would also couple AC current from
the primary to the secondary. A grounded Faraday shield between
the primary and the secondary greatly reduces the coupling of
common-mode noise. This may be another winding or a metal strip
surrounding a winding. Differential noise can magnetically couple
from the primary to the secondary of an isolation transformer, and
must be filtered out if a problem.
APPLICATIONS OF TRANSFORMER
ISOLATION
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Pulse transformers
Some small transformers are used for isolation in pulse circuits.
Electronics Testing
In electronics testing and servicing an isolation transformer is a 1:1
(under load) power transformer used for safety. Without it, exposed
live metal in a device under test is at a hazardous voltage relative to
grounded objects such as a heating radiator or oscilloscope ground
lead (a particular hazard with some old vacuum-tube equipment
with live chassis). With the transformer, as there is no conductive
connection between transformer secondary and earth, there is no
danger in touching a live part of the circuit while another part of
the body is earthed.
OPTICAL ISOLATION
Why optical isolation is needed?
Gustav Hertz discovered that particular surfaces liberated electrons
when influenced by light. Subsequent work by Albert Einstein in
the early 19s established that bundles of light energy, called
"photons", could transfer their energy to free electrons and liberate
them from metal surfaces in a mathematically predictable way. The
application of this "photoelectric phenomenon" to the field of
semiconductors is the basis for optical isolation.
OPTICAL ISOLATION
The Basic Theory Optical isolation has two basic elements: a light
source (usually a light emitting diode) and a photo-sensitive
detector. These two elements are positioned facing one another
and inserted in an electrical circuit to form an optocoupler. The key
property of an optocoupler is that there is a insulating gap between
the light source and the detector. No current passes through this
gap, only the desired light waves representing data. Thus the two
sides of the circuit are effectively "isolated" from one another.
Primary Application In data communications, the primary
application for optical isolation is in a point-to-point data circuit
that covers a distance of several hundred feet or more. Because the
connected devices are presumably on different power circuits, a
ground potential difference likely exists between them. When such
a condition exists, the voltage of "ground" can be different,
sometimes by severalhundred volts.
OPERATION OF OPTICAL ISOLATION
Where a ground potential difference exists, a phenomenon called
ground looping can occur. In this phenomenon, current will flow
along the data line in an effort to equalize the ground potential
between the connected devices. Ground looping can, at the very
least, severely garble communications--if not damage hardware!
Optical isolation solves the problem of ground looping by effectively
lifting the connection between the data line and "ground" at either
end of the line. If an optically coupled connection exists at each
end, the data traffic "floats" above the volatility of ground potential
differences.
APPLICATION OF OPTICAL ISOLATION
It might seem at first glance that a device that allows light to flow in
only one direction would violate Kirchhoff's law and the second law
of thermodynamics, by allowing light energy to flow from a cold
object to a hot object and blocking it in the other direction, but the
violation is avoided because the isolator must absorb (not reflect)
the light from the hot object and will eventually reradiate it to the
cold one. Attempts to re-route the photons back to their source
unavoidably involve creating a route by which other photons can
travel from the hot body to the cold one, avoiding the paradox.
CONCLUSION
So, this power point presentation has illuminated the feature of
isolation. We saw how isolation is used in real time applications.
THANK YOU