ELECTRICAL THINGS

Different parts of the transformer are:- Transformer tank High voltage and low voltage bushings Cooling tubes / Fins / Radiator banks Cooling fans Conservator tank  Explosion vent Oil drain valve Oil inlet / filling valve Temperature / Pressure gauges Name plate Control panel and tap changer Transformer Tank The entire core and coil assembly of oil filled transformer is enclosed by metal tank made mostly of welded mild steel sheets or sometimes aluminum . Purpose of the tank is to hold the oil and to provide a protective causing around the internal parts. The tank is earthed so as to prevent external bodies from getting electrocuted and to prevent electromagnetic noise to escape from inside the transformer and interfere with outside equipments in the vicinity of the transformer. Transformer tanks must be air-tightly sealed for it to isolate its content from any atmospheric contaminants. Sufficient clearances are kept between the outer surface of outermost winding and inside walls ...

  Insulating Parts Insulation is essential to isolate the live parts inside a transformer from other live parts at different potential or from the grounded parts.   The desirable properties of an insulation material are: High resistivity High breakdown voltage (breakdown strength) High dielectric constant ( ɛ r ) Low dissipation factor (tan 𝛿) Thermal stability Chemical stability Mechanical stability The different MAJOR insulations in a transformer are: Between core and LV (press board) Between LV and HV (impregnated press board, oil) Between top and bottom of winding and yoke (impregnated press board) Between HV and tank (impregnated paper, cotton, oil) Bushings (Porcelain)- used to take out HV and LV coil terminals from inside the tank for external connections to overhead lines. The different MINOR insulations in a transformer are: Between conductors (enamel, varnish) Between turns (impregnated paper, cotton) Between layers (impregnated paper, cotton, press board) Between l...

Windings Electrical Parts of a transformer comprise mainly of the primary and secondary windings. The windings consist of the current-carrying conductors wound around the sections of the core, and these must be properly insulated, supported and cooled to withstand operational and test conditions. Copper and Aluminum are the primary materials used as conductors in power transformer windings. These conductors may be of circular or rectangular cross-section, depending on the current and voltage ratings of the machine and are insulated using enamel, paper, or cotton. Desirable properties of a conducting material for use in transformer ( or any Electrical Machine ) are:- High Conductivity Low temperature coefficient of resistance  High Thermal Conductivity Low coefficient of thermal expansion High ductility High tensile strength Not too heavy Low corrosion by chemicals The two materials mostly commonly used for windings of transformers are copper and aluminum . Both have their relative...

According to the type of core construction, transformers are distinguished as:- Core type transformer Shell type transformer Core type Transformer In Core type construction, the magnetic core is built of laminations to form a rectangular frame and the coils are arranged concentrically around limbs of the core. The magnetic circuit of the Transformer has reluctances connected in series as shown below:- Single-Phase, Core type Transformer Core type Transformer has the following features: Less amount of insulation required Mechanically bad More amount of Copper (Cu) required Used for high voltage application Inter leaving windings preferred Equal Cross Section Area of both the limbs Low current rating Small KVA rating Shell Type Transformer Here the two windings are wound on same limb i.e. middle limb of the core. Hence, the windings are surrounded on both sides by the core. The magnetic circuit of the transformer has reluctances connected in parallel as shown below: Single-Phase, Shell t...

  Construction details of Transformer Major Construction parts of a transformer can be categorized as:- Magnetic parts Insulating parts Electrical parts Mechanical parts and accessories Magnetic parts In a Transformer the primary and secondary windings are wound around the core of a transformer. Core is a magnetic material which allows the flow of magnetic flux lines to link both primary and secondary winding. Two basic functions of the core are: To provide an easy path for the magnetic flux to flow through it, and thereby link both primary and secondary windings. To provide mechanical support for holding the coils. Both primary and secondary coils are wounded over and around the core. There are certain properties that the core material must satisfy: Core should have low reluctance and high permeability to the flow of magnetic flux. Core is generally made of Silicon steel. Features of Silicon Steel : Ferrous Magnetic Material Low reluctance and high permeability  Low hysteresi...

  Magnetic Circuits A magnetic circuits can be defined as the path which is followed by magnetic flux. An example of magnetic circuit is given below:- The Core is made of iron. Iron being a good magnetic material (high value of relative permeability), flux produced by the iron core will entirely pass through the iron core and thus magnetic field intensity(H) can be assumed to remain fixed at every point within the iron core. Magnetic field intensity developed by the iron core, H c = Ni  / l c    AT/m Flux density within the iron core, B c = μ o  μ r  H c    Wb/m^2 where μ r is the relative permeability of iron material used in the iron core. The amount of flux flowing through the iron core,  Ⲫ c = B.A c or,  Ⲫ c = μ o  μ r  H c A c or,  Ⲫ c = μ o  μ r (Ni  / l c ) A c or,  Ⲫ c = Ni  /( l c / μ o  μ r  A c ) or,  Ⲫ c = Ni  / S Product of number of turns (N) in the coil and cur...

The transformer is a device that transfers electrical energy from one electrical circuit to another electrical circuit through the medium of magnetic field and without the change of frequency. The electrical circuit that receives energy from the source is called as Primary winding and other circuit that delivers electrical energy to load is called as Secondary winding. The Primary and Secondary windings of a transformer are coupled magnetically i.e. the electrical energy input to the transformer is first converted to magnetic energy and then this magnetic energy is again converted to electrical energy by the secondary winding to be delivered to load. Transformers are static electromagnetic devices in which transformation of voltage and current or both occurs without any change in frequency, but no transformation of energy takes place. Transformers work on the principle of electromagnetic induction, i.e. mutual coupling between two coils. Transformer does not have any moving parts so ou...