Đang chuẩn bị liên kết để tải về tài liệu:
Transformer Engineering - Design and Practice Episode 4

Tham khảo tài liệu 'transformer engineering - design and practice episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 2 Magnetic Characteristics The magnetic circuit is one of the most important active parts of a transformer. It consists of laminated iron core and carries flux linked to windings. Energy is transferred from one electrical circuit to another through the magnetic field carried by the core. The iron core provides a low reluctance path to the magnetic flux thereby reducing magnetizing current. Most of the flux is contained in the core reducing stray losses in structural parts. Due to on-going research and development efforts 1 by steel and transformer manufacturers core materials with improved characteristics are getting developed and applied with better core building technologies. In the early days of transformer manufacturing inferior grades of laminated steel as per today s standards were used with inherent high losses and magnetizing volt-amperes. Later on it was found that the addition of silicon content of about 4 to 5 improves the performance characteristics significantly due to a marked reduction in eddy losses on account of the increase in material resistivity and increase in permeability. Hysteresis loss is also lower due to a narrower hysteresis loop. The addition of silicon also helps to reduce the aging effects. Although silicon makes the material brittle it is well within limits and does not pose problems during the process of core building. Subsequently the cold rolled manufacturing technology in which the grains are oriented in the direction of rolling gave a new direction to material development for many decades and even today newer materials are centered around the basic grain orientation process. Important stages of core material development are non-oriented hot rolled grain oriented HRGO cold rolled grain oriented CRGO high permeability cold rolled grain oriented Hi-B laser scribed and mechanically scribed. Laminations with lower thickness are manufactured and used to take advantage of lower eddy losses. Currently the lowest thickness available is .