Atanasov, A., I. Valtchev, D. Kolevska, and S. Valtchev,
"Experimental Research of the Boron Nitride Diffusion",
Elektropromishlenost i Priborostroene (now: Elektrotechnica & Elektronica), no. 1, pp. 31–35, January, 1978.
vanWesenbeeck, M. P. N., J. B. Klaassens, U. vonStockhausen, A. M. D. Anciola, and S. S. Valtchev,
"A multiple-switch high-voltage DC-DC converter",
IEEE Transactions on Industrial Electronics, vol. IE-44, no. 6: IEEE, pp. 780–787, December, 1997.
AbstractSeries connection of power devices has evolved into a mature technique and is widely applied in HV dc systems. Static and dynamic voltage balance is ensured by shunting individual devices with dissipative snubbers. The snubber losses become pronounced for increased operating frequencies and adversely affect power density. Capacitive snubbers do not exhibit these disadvantages, but they require a zero-voltage switching mode. Super-resonant power converters facilitate the principle of zero-voltage switching. A high-voltage dc-dc power converter with multiple series-connected devices is proposed. It allows the application of nondissipating snubbers to assist the voltage sharing between the multiple series-connected devices and lowers turn-off losses. Simulation results obtained with a circuit simulator are validated in an experimental converter operating with two series-connected devices. The behavior of the series connection is examined for MOSFET's and insulated gate bipolar transistors (IGBT's) by both experimental work with a 2-kW prototype and computer simulation. Applications can be found in traction and heavy industry, where the soft-switching converter is directly powered from a high-voltage source.
Pina, J., P. Pereira, S. Valtchev, A. Gonçalves, V. M. Neves, A. Alvarez, and L. Rodrigues,
"A test rig for thrust force measurements of an all HTS linear synchronous motor",
Journal of Physics: Conference Series, vol. 97: IOPScience, pp. 012220, 2008.
AbstractThis paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductor's ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.