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... 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 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.

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