Transformer Engineering

Design, Technology, and Diagnostics, Second Edition

S.V. Kulkarni, S.A. Khaparde

• Editore: CRC Press
• Anno: 2017
• ISBN:
  9781351833226
• Edizione: 2
• Argomento: Technology & Engineering
• Categoria: Electrical Engineering & Telecommunications

Transformer Engineering: Design, Technology, and Diagnostics, Second Edition helps you design better transformers, apply advanced numerical field computations more effectively, and tackle operational and maintenance issues. Building on the bestselling Transformer Engineering: Design and Practice, this greatly expanded second edition also emphasizes diagnostic aspects and transformer-system interactions.

What's New in This Edition

• Three new chapters on electromagnetic fields in transformers, transformer-system interactions and modeling, and monitoring and diagnostics
• An extensively revised chapter on recent trends in transformer technology
• An extensively updated chapter on short-circuit strength, including failure mechanisms and safety factors
• A step-by-step procedure for designing a transformer
• Updates throughout, reflecting advances in the field

A blend of theory and practice, this comprehensive book examines aspects of transformer engineering, from design to diagnostics. It thoroughly explains electromagnetic fields and the finite element method to help you solve practical problems related to transformers. Coverage includes important design challenges, such as eddy and stray loss evaluation and control, transient response, short-circuit withstand and strength, and insulation design. The authors also give pointers for further research. Students and engineers starting their careers will appreciate the sample design of a typical power transformer.

Presenting in-depth explanations, modern computational techniques, and emerging trends, this is a valuable reference for those working in the transformer industry, as well as for students and researchers. It offers guidance in optimizing and enhancing transformer design, manufacturing, and condition monitoring to meet the challenges of a highly competitive market.

1

Transformer Fundamentals

1.1 Perspective

Transformers are static devices that transfer electrical energy from one circuit to another by the phenomenon of electromagnetic induction without any change in frequency. They can link circuits that have different voltages, which is one of the enabling factors for the universal use of the alternating current (AC) system for the transmission and distribution of electrical energy. Hence, transformers ensure that various components of the power system, viz. generators, transmission lines, distribution networks and loads, can all be operated at their most suitable voltage levels. As transmission voltages are increased to higher levels in some parts of a power system, transformers again play a key role in interconnecting the different parts of the system at different voltage levels. Transformers are therefore vital links between the generating stations and the points of utilization in any system.

The transformer is an electromagnetic conversion device in which the electrical energy received by its primary winding is first converted into magnetic energy, which is re-converted into 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 either a step-up or a step-down transformer depending upon whether the secondary voltage is higher or lower than the primary voltage. 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 instead of primary/secondary windings.

Magnetic circuits: A transfer of electrical energy between two circuits takes place through a transformer without the use of moving parts; a transformer therefore has higher efficiency and lower maintenance cost than rotating electrical machines. Better grades of materials for cores are continuously being developed and introduced. Different types of silicon steels have been introduced in the following chronological order: non-oriented, hot-rolled grain oriented, cold-rolled grain oriented (CRGO), Hi-B, mechanically scribed and laser scribed. The last three types are improved versions of the CRGO class of materials. The saturation flux density has remained more or less constant around 2.0 Tesla for the CRGO grades; however, the sophisticated technologies and processes used while manufacturing the better grades have resulted in significant improvements in the watts/kg and volt-amperes/kg characteristics in the rolling direction. Transformer designers have a limited choice of grades of material; for a grade chosen based on a cost-benefit analysis, the performance of the core can be further optimized by using efficient design and manufacturing technology. The non-mitred construction used earlier was replaced by a better mitred type many decades ago, and now a far superior step-lap construction is almost universally used. A considerable increase in energy costs over the years is mainly responsible for the development (and consequent increase in the use) of the better grades of material for cores: these not only reduce the core loss ...