Transient phenomena in power transformers theoretical and practical approach
In recent decades the theoretical and experimental study of transient phenomena regarding power transformers has experienced a great development. Results of these studies allowed the elucidation of the main theoretical and practical aspects of the transient phenomena due to propagation of impulse voltages inside the transformers. These studies increased the safe operation of power transformer and led to the introduction of rational insulation usage and also helped to develop efficient protection measures.
Calculation methods for lightning impulse voltage distribution in power transformers
This paper aims to develop and update the methodology for calculating the stress to which the internal insulation of power transformer is subjected during lightning impulse test. Power transformer internal isolation consists of insolating intervals of oil impregnated paper, transformer board and oil. In whole, the transformer's insulation must withstand the voltage testing levels prescribed by the standards. One of the methods for determining the internal stress of various parts of the power transformer's insulation is by using mathematical models.
Coherent pulsed injection seeding of two gain-switched semiconductor lasers
High-power, narrow-spectrum, short pulses at a wavelength near 830 nm are needed for optical logic applications. The authors report the generation of two coherent trains of pulses by pulsed injection seeding of two gain-switched semiconductor lasers with one mode-locked master oscillator. The available power was doubled and both lasers emit in nearly identical spectral lines. Short pulses (30-50 ps) are generated at a repetition rate of 1.9 GHz. The spectrum is reduced to a single mode cluster and shows a 1.7 AA wide chirp suitable for pulse compression. The peak power is 0.1 W for each pulse train. The capability of this technique for coherent power combining is demonstrated.<<ETX>>