3. TRANSFORMER:
An A.C. device used to change high voltage low current
A.C. into low voltage high current A.C. and vice-versa
without changing the frequency.
In brief,
1. Transfers electric power from one circuit to another.
2. It does so without a change of frequency.
3. It accomplishes this by electromagnetic induction.
4.Where the two electric circuits are in mutual inductive
influence of each other.
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4. PRINCIPLE OF OPERATION:
Transformer works on
the principle of mutual
induction of two coils.
When current in the
primary coil is changed
the flux linked to the
secondary coil also
changes. Consequently
an EMF is induced in
the secondary coil.
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6. 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.
In theory, the definition of ‘isolation transformer’ applies to
any transformer where there is no direct connection between
the primary and the secondary windings. In other words: all
transformers which are not autotransformers. The windings
are connected only by the magnetic flux in the core.
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7. 1. An isolation transformer allows you to establish a
separate earth ground...a true earth ground.
2. Isolation transformers are often used to isolate the
machine or equipment from the rest of the electrical
installation, to avoid loss of power in the case of a
first insulation fault.
3. Suitably designed isolation transformers block
interference caused by ground loops.
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8. 4. Isolation transformers with electrostatic shields are
used for power supplies for sensitive equipment such as
computers, medical devices, or laboratory instruments.
5. Isolation transformers can be used to protect people
against the dangers of electric shocks.
6. Isolation transformers block transmission of the DC
component in signals from one circuit to the other, but
allow AC components in signals to pass.
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9. APPLICATIONS
A. MEDICAL TRANSFORMERS:
1. Medical transformers are designed:
2. To isolate the patient and/or the operator from an
electric shock
3. To protect the equipment from power surges or
faulty components
B. PROTECTION OF SENSITIVE EQUIPMENT.
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11. 1. An opto-isolator or optocoupler is used for
providing optical isolation.
2. An optical isolator, or optocoupler, is an optical
component which allows the transmission of light in
only one direction. It is typically used to prevent
unwanted feedback into an optical oscillator, such as
a laser cavity.
3. Opto-isolators prevent high voltages from affecting
the system receiving the signal.
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12. 4. An opto-isolator, also called an optocoupler,
photocoupler, or optical isolator, is a component that
transfers electrical signals between two isolated
circuits by using light.
5. A common type of opto-isolator consists of an LED and
a phototransistor in the same opaque package.
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13. 6. An opto-isolator contains a source (emitter) of
light(LED), that converts electrical input signal into
light, a closed optical channel and a photosensor,
which detects incoming light and either generates
electric energy directly, or modulates electric
current flowing from an external power supply.
7. The LED converts the incoming electrical signal into
light and the photosensor detects the incoming light
and generates electric energy. There is no direct
connection between the LED and photo transistor,
they are isolated optically i.e. through light.
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14. 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 an 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.
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 several
hundred volts.
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15. 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 damages
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
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16. Optical Isolation vs. Transformer Isolation A common belief is that
optical isolation is superior to transformer isolation in every case.
Theoretically this is true, because optical isolation provides a
"true" physical barrier, whereas transformer isolation is a coupling
designed to merely "absorb" unwanted frequencies. However, in
practice optical isolation is a less efficient transmitter of energy
than transformer isolation--an important consideration when
signal strength is an issue. Therefore transformer isolation is
sometimes the best choice for very long-distance applications. And
optical isolation also becomes a prohibitively expensive solution at
higher data rates. So in the real world, transformer isolation still
has its place.
OPTICAL ISOLATION VS.
TRANSFORMER ISOLATION
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17. ADVANTAGES:
1. Opto – isolators can withstand input-output voltages
upto 10kV and voltage transients speed of 10kV / us.
2. They are capable of wideband signal transmission.
3. They work faster in comparison of isolation
transformers.
4. They eliminate problems like noise and transient.
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