Chapter -1
INTODUCTION
A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. Electromagnetic induction produces an electromotive force within a conductor which is exposed to time varyingmagnetic fields. Transformers are used to increase or decrease the alternating voltages in electric power applications.
1.1 History
the principle of the operation of the transformer, was discovered independently by Michael Faraday in 1831, Joseph Henry in 1832. The relationship between EMF and magnetic flux is an equation now known as Faraday's law of induction.
here is the magnitude of the EMF in Volts and ΦB is the magnetic flux through the circuit in webers
Preceded by Francesco Zantedeschi in 1830, Faraday performed early experiments on induction between coils of wire, including winding a pair of coils around an iron ring, thus creating the first toroidal closed-core transformer. However he only applied individual pulses of current to his transformer, and never discovered the relation between the turns ratio and EMF in the windings. Presently, toroidal power transformers are manufactured with dual primary coils and dual secondary coils, allowing for a high degree of input and output voltage flexibility.
Faraday's experiment with induction between coils of wire Faraday's ring transformer
1.2 Optimum Design of Cross – Section of Transformer Core
The maximum flux density of CRGO steel is about 1.9 Tesla. Means the steel becomes saturated at the flux density 1.9 Tesla. One important criteria for the design of transformer core, is that, it must not be saturated during the transformer’s normal operation mode. Voltages of transformer depend upon its total magnetizing flux. Total magnetizing flux through core is nothing but the product of flux density and cross – sectional area of the core. Hence, flux density of a core can be controlled by adjusting the cross sectional area of the core during its design.
The ideal shape of cross-section of a transformer core is circular. For making perfect circular cross section, each and every successive lamination steel sheet should be cut in different dimension and size. This is absolutely uneconomical for practical manufacturing.
Oil ducts are needed for cooling the core. Cooling ducts are necessary because hot-spot temperature may rise dangerously high and their number depends on the core diameter and materials that get used for core.. The steel sheet lamination blocks, oil ducts, and clamping plates; all should lie within the peripheral of optimum core circle.
1.3 Manufacturing of Transformer
During core manufacturing in factory some factors are taken into consideration
• Higher reliability.
• Reduction in iron loss in transformer and magnetizing current.
• Lowering material cost and labor cost.
• abatement of noise levels.
Chapter 2
Design: Analysis, Design Methodology
2.1 Design: Analysis
In operation the C.T. will induce current in its secondary winding and burden which serves to completely oppose the magnetising effect of the primary current, except for that small proportion required to magnetise the core. This core magnetising component will then be the only source of error if the secondary current is to be used as a measure of the primary current.
The angle θ is so small as to allow the approximations I1 N2 + Iw and θ = Ir / I1 radians, i.e. the current error is due to the watt loss component of the excitation current and the phase error is proportional to the reactive component Ir . The ratio error can be corrected by an amendment to the turns ratio, the secondary winding being reduced by several turns or fractions of a turn. Because of the non – linearity of the excitation characteristics, such corrections do not maintain accuracy as the current changes, and a choice must be made which gives good balance over the whole range of current.
2.2 Design Methodology
With the rapid development of digital computers, designers are no longer obliged to perform routine calculations. Computers are widely used for optimization of transformer design. Within a matter of seconds,
today’s computers can work out a number of designs (by varying flux density, core dimensions, current density, etc) and come up with an optimum transformer design.The proposed transformer design methodologyis implemented in a software package, creating a suitable graphical user interface in which the user can set the values of the input parameters. This graphical user interface provides interactive and intuitive visual communication to transformer designers, enhancing the abilities of engineers to conduct studies with ease and flexibility. It is important to note that a database incorporating standard values for the components of a transformer is linked to the program in order to calculate all the necessary characteristics, such as the unit costs of the transformer materials, the dimensions of the conductors for the primary and secondary windings, coefficients of panel losses, tank convention and tank radiation constants, and so on. When the user chooses the desirable input parameters, the software finds a number of acceptable solutions that are stored into a database. This database is created automatically in every execution of the program where the user has the opportunity to find the technical characteristics of each acceptable solution, including the cheapest one.
Chapter 3
FAILURE ANALYSIS OF TRANSFORMER
3.1Causes of the failure of a transformer
To track the cause of the failure is the first step to formulate its solution.
The origin of the defects is not simple. Generally, it is the combination of many factors that can be classified in the following way
1. Imperfection on the specifications
• Mistake in the selection of the type of insulation.
• Not appropriate capacity.
• Lack of attention to the conditions in the place of installation (dampness, temperature, dangerous gases, etc)
2. Imperfection on the facilities
• Wrong installation.
• Wrong capacity and protection range of lightning rods
• Switch and relay for protection is wrong.
3. Imperfections on the operation and maintenance of the equipment
• External conducting parts loose and heating up of the same.
• Deterioration of the insulating oil
• Excessive load or mistakes in the connection of the cables.
• Mistake in the operation, and carelessness in the arrangement of the protection circuits.
• Insufficient inspection of the gaskets and valves.
• Poor maintenance of the accessories. Abnormal voltage
4. Normal wear and tear
5. Natural disasters
3.2Types of failures
3.2.1 Internal failures of the transformer: in core and coil
• Dielectric interruption
• Rupture and twist of the winding
• Mistake on the grounding
• Open connection of tap changer
• Insulating oil
` 3.2.2 External defects of the transformer:
• In the tank
• Due to oil leaks in the gasket, valve, or weld cord
• Due to the bushings of the breathers, over pressure valve, thermometers, oil level gauge, etc.
• Defects on the forced cooling fans, Buchholz Relay, exit of the current transformers of the bushings, etc.
Chapter 4
Why use Design Software??
There is only one reason to use any software package, including transformer design software, and that is to have another tool in your company to help you increase profits. So the question really is, "How will the transformer design software help you make money?"
1. Material Savings:
Because of the software design and the ease of making multiple iterations of the same design, it is easy to optimize the transformer design to use a minimum of expensive materials. You can customize the design to meet you own inventory needs using wire sizes and steel grades that cost less for you to purchase and are best for easy production.
2. Time Savings:
Engineering time required to complete a design is reduced to mere minutes. This is especially valuable when you need to get quick and accurate quotations to your potential customers.
3. Error Free:
Because all calculations are done within the program, human errors are eliminated which in turn eliminate costs associated with these. This aspect is also very important to the productive capacity of your design engineers as design stress is alleviated.
4. Prototypes Eliminated:
The software gives you the opportunity to simulate the designed transformer under varying conditions and observe how the transformer will react under those conditions. You will obtain information exactly as if you had built a prototype and made actual measurements in your own laboratory. Therefore, until you have a design iteration that meets all of your requirements you do not need to build any test transformers. Eliminating expensive prototypes will have a real positive effect on your final profits.
5. Documentation:
The software immediately generates three important pages when your design is completed. The first page gives you detailed input data with a schematic. The second page provides details on the Mechanical Part including the bobbin, core and windings. The third page provides details on the electrical, magnetic, and thermal data (nominal, no-load, short circuit, and duty cycle operations). Some of this documentation can be used immediately to accompany customer quotations thereby eliminating the need to create time consuming and difficult documentation just for a quote. The Rale software also gives you the option to create your own pages in your own format for production requirements
Chapter 5
Results
5.1 Optimizing transformer design
Transformers are regarded as critical components in power systems. Market globalization has led to the necessity of being increasingly competitive in designing transformers. Manufacturers are adopting design strategies that produce rapid, optimal, reliable and feasible transformers at lower costs. Opera offers the tool for integrating finite elements into the design process of electromagnetic devices, thus simplifying the challenge faced by researchers and design engineers.
5.2Introduction to Transformer Design
Today’s designers of transformers and reactors are being pressured to deliver more efficient devices in ever-shortening timescales. In this Vector Fields software division will show how the Suite can be used to deliver the accuracy of Finite Element Analysis with the ease-of-use of analytical design packages.
5.3Validation of Magnetic Field Analysis with Vector Hysteresis
A test case for validating 2D and 3D magnetic field analysis codes, including hysteresis, is presented. For this purpose, an experimental set-up constituted by a three limbed ferromagnetic core fitted with pick-up coils has been especially designed and built.
Chapter 6
Standard results include
• Efficiency
• Inductances
• Saturation curves
• Short-circuit analysis
• Open-circuit analysis
• Inrush current/load test
• Switch on transients
• Losses – copper, eddy-current, hysteresis
• Stray field/shielding analysis (EMC/EMI)
• Dynamic forces on coils
Chapter 7
CAPABLITIES
With manufacturers of power systems and associated devices who design products to meet the demands of the modern world, can increase efficiency and develop a smaller footprint, with lower environmental impact. these often competing requirements, enabling successful design of innovative and highly optimised products. As the conventional development process of design iterations and physical proto-type build/test becomes both time consuming and costly, designer
• 2d and 3d device evaluation using advanced Finite Element simulation
• Full non-linear and locally orthotropic material representations for both electromagnetics & thermal
• Accuracy comparable with measurement
• Rapid testing of design variants
• Include the power supply and load
• Include thermal and structural analysis
Chapter 8
FUTURE WORK
IN FUTURE WE IMPLIMENT THIS EXCEL SHEET IN TO THE VBA LANGUAGE WHICH ABLE:
(1) Enable user to use the program interactively and carries out calculation and selection of the most optimized design. This would make the product more competitive. Review of Development done in Computerization of Electrical Specifications for Transformers.
(2) Majority of intuitive data would be standardized and would enable the new design engineer to generate equally competitive designs.
(3) After the development there would be considerable reduction in errors and this would result in decrease in rework and rejection at shop floor and thereby increased in shop floor productivity also.
(4) The overall accuracy in Designing Electrical Specifications for Transformers would improve and lead to a fault free design.
(5) This would form the basis for company’s new design standards and practices, in terms of Product planning and development.
(6) The approach incorporated for the said Project will gain significant momentum, in terms of Product planning and development and can benefit the manufacturing set-up as a whole, thus making the company to move towards its ultimate goal leading to sustainability and profitability
CHAPTER 9
CONCLUSION
There is a growing need in the manufacturing industry sector to gain insight into the significant aspects and parameters to apply new concepts of product design and development.
The Development of an Integrated System for Electrical Specifications Generation of Transformers in EXCEL would benefit the entire industry. This would not only improve productivity but also contribute towards quality, accuracy and design automation
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