By Mohammed AboAjmaa SDU T.C SÜLEMAN DEMİREL UNIVERSITY FEN BİLİMLERİ ENSTİTÜSÜ Mühendislik fakültesi ELEKTRONİK VE HABERLEŞME MÜHENDİSLİĞİ Electromagnetic Waves Theory A COURSE OFFERED BY Prof. Dr. Mustafa MERDAN RANSFORMER T REPORT ABOUT Submitted by MSc. Student Mohammed Mahdi AboAjamm Student No. 1330145006
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By Mohammed AboAjmaa SDU
T.C
SÜLEMAN DEMİREL UNIVERSITY
FEN BİLİMLERİ ENSTİTÜSÜ
Mühendislik fakültesi
ELEKTRONİK VE HABERLEŞME
MÜHENDİSLİĞİ
Electromagnetic Waves Theory
A COURSE OFFERED BY
Prof. Dr. Mustafa MERDAN
RANSFORMERTREPORT ABOUT
Submitted by
MSc. Student
Mohammed Mahdi AboAjamm
Student No. 1330145006
By Mohammed AboAjmaa SDU
TRANSFORMER
What is Transformer?
A transformer is a static device that transfers electrical energy from
one circuit to another by electromagnetic induction without the
change in frequency. The transformer, which can link circuits with
different voltages, has been instrumental in enabling universal use
of the alternating current system for transmission and distribution
of electrical energy. Various components of power system, viz.
generators, transmission lines, distribution networks and finally the
loads, can be operated at their most suited voltage levels. As the
transmission voltages are increased to higher levels in some part
of the power system, transformers again play a key role in
interconnection of systems at different voltage levels.
Transformers occupy prominent positions in the power system,
being the vital links between generating stations and points of
utilization.
By Mohammed AboAjmaa SDU
The transformer is an electromagnetic conversion device in which
electrical energy received by primary winding is first converted into
magnetic energy which is reconverted back into a useful electrical
energy in other circuits (secondary winding, tertiary winding, etc.).
Thus, the primary and secondary windings are not connected
electrically, but coupled magnetically. A transformer is termed as
either a step-up or step-down transformer depending upon
whether the secondary voltage is higher or lower than the primary
voltage, respectively. Transformers can be used to either step-up
or step-down voltage depending upon the need and application;
hence their windings are referred as high-voltage/low-voltage or
high-tension/low-tension windings in place of primary/secondary
windings. links between generating stations and points of
utilization.
By Mohammed AboAjmaa SDU
Magnetic circuit:
Electrical energy transfer between two circuits takes place through a transformer without the use of moving parts; the transformer therefore has higher efficiency and low maintenance cost as compared to rotating electrical machines. There are continuous developments and introductions of better grades of core material. The important stages of core material development can be summarized as: non-oriented silicon steel, hot rolled grain oriented silicon steel, cold rolled grain oriented (CRGO) silicon steel, Hi-B, laser scribed and mechanically scribed. The last three materials are improved versions of CRGO. Saturation flux density has remained more or less constant around 2.0 Tesla for CRGO; but there is a continuous improvement in watts/kg and volt-amperes/kg characteristics in the rolling direction. The core material developments are spearheaded by big steel manufacturers, and the transformer designers can optimize the performance of core by using efficient design and manufacturing technologies. The core building technology has improved from the non-mitred to mitred and then to the step-lap construction. A trend of reduction of transformer core losses in the last few years is the result of a considerable increase in energy costs. The better grades of core steel not only reduce the core loss but they also help in reducing the noise level by few decibels. Use of amorphous steel for transformer cores results in substantial core loss reduction (loss is about one-third that of CRGO silicon steel). Since the manufacturing technology of handling this brittle material is difficult, its use in transformers is not widespread.
By Mohammed AboAjmaa SDU
Windings:
The rectangular paper-covered copper conductor is the most commonly used conductor for the windings of medium and large power transformers. These conductors can be individual strip conductors, bunched conductors or continuously transposed cable (CTC) conductors. In low voltage side of a distribution transformer, where much fewer turns are involved, the use of copper or aluminum foils may find preference. To enhance the short circuit withstand capability, the work hardened copper is commonly used instead of soft annealed copper, particularly for higher rating transformers. In the case of a generator transformer having high current rating, the CTC conductor is mostly used which gives better space factor and reduced eddy losses in windings. When the CTC conductor is used in transformers, it is usually of epoxy bonded type to enhance its short circuit strength. Another variety of copper conductor or aluminum conductor is with the thermally upgraded insulating paper, which is suitable for hot-spot temperature of about 110°C. It is possible to meet the special overloading conditions with the help of this insulating paper. Moreover, the aging of winding insulation material will be slowed down comparatively. For better mechanical properties, the epoxy diamond dot paper can be used as an interlayer insulation for a multi-layer winding. High temperature superconductors may find their application in power transformers which are expected to be available commercially within next few years. Their success shall depend on economic viability, ease of manufacture and reliability considerations.
By Mohammed AboAjmaa SDU
Insulation and cooling:
Pre-compressed pressboard is used in windings as opposed to the softer materials used in earlier days. The major insulation (between windings, between winding and yoke, etc.) consists of a number of oil ducts formed by suitably spaced insulating cylinders/barriers. Well profiled angle rings, angle caps and other special insulation components are also used. Mineral oil has traditionally been the most commonly used electrical insulating medium and coolant in transformers. Studies have proved that oil-barrier insulation system can be used at the rated voltages greater than 1000 kV. A high dielectric strength of oil-impregnated paper and pressboard is the main reason for using oil as the most important constituent of the transformer insulation system. Manufacturers have used silicon-based liquid for insulation and cooling. Due to non-toxic dielectric and self-extinguishing properties, it is selected as a replacement of Askarel. High cost of silicon is an inhibiting factor for its widespread use. Super-biodegradable vegetable seed based oils are also available for use in environmentally sensitive locations. There is considerable advancement in the technology of gas immersed transformers in recent years. SF6 gas has excellent dielectric strength and is nonflammable. Hence, SF6 transformers find their application in the areas where firehazard prevention is of paramount importance. Due to lower specific gravity of SF6 gas, the gas insulated transformer is usually lighter than the oil insulated transformer. The dielectric strength of SF6 gas is a function of the operating pressure; the higher the pressure, the higher the dielectric strength. However, the heat capacity and thermal time constant of SF6 gas are smaller than that of oil, resulting in reduced overload capacity of SF6 transformers as compared to oilimmersed transformers. Environmental concerns, sealing problems, lower cooling capability and present high cost of manufacture are the challenges which have to be overcome for the widespread use of SF6 cooled transformers.
By Mohammed AboAjmaa SDU
PRINCIPLES For Transformer:
It is very common, for simplification or approximation purposes, to
analyze the transformer as an ideal transformer model as
represented in the two images. An ideal transformer is a
theoretical, linear transformer that is lossless and
perfectly coupled; that is, there are no energy losses and flux is
completely confined within the magnetic core. Perfect coupling
implies infinitely high core magnetic permeability and winding
inductances and zero net magneto motive force. varying current in
the transformer's primary winding creates a varying magnetic flux
in the core and a varying magnetic field impinging on the
secondary winding. This varying magnetic field at the secondary
induces a varying electromotive force(EMF) or voltage in the
secondary winding. The primary and secondary windings are
wrapped around a core of infinitely high magnetic permeability[d]
so that all of the magnetic flux passes through both the primary
and secondary windings with a voltage connected to theprimary
winding and load impedance connected to the secondary winding
the transformer currents flow in the indicated directions. (See also
Polarity.)
According to Faraday's law of induction, since the same magnetic
flux passes through both the primary and secondary windings in an
ideal transformer, a voltage is induced in each winding], according