Magnetic Circuit of a High-Voltage Transformer up to 10 kHz

Abstract

Power and energy measurements in smart grids require a measurement system capable of performing signal processing at the higher harmonic frequencies that are present in power grids. For the calibration process of instrument voltage transformers, or high-voltage dividers, it is necessary to have a high-voltage source with an appropriate frequency range. The fundamental element of such a source is the output high-voltage transformer operating at a nominal voltage of 10 kV and in the frequency range from 200 Hz up to 10 kHz. The output current is assumed to be lower than 20 mA. This paper focuses on the design and realization of the magnetic circuit of the transformer described above. Trafoperm, ferrite or nanocrystalline materials can be used for the frequency range considered here. Ferrite materials usually reach saturation at a magnetic flux density of 0.2 T with very low permeability values, while trafoperm material usually suffers from unacceptable power losses in higher frequency areas. This is the main reason why these materials are not suitable for use in a wide range of frequencies, and some combined magnetic cores must be used. The proposed solution is based on magnetic cut C type cores made from nanocrystalline alloy (VITROPERM 500), which behaves better in the frequency range under consideration. The magnetic parameters of this material were measured and compared with trafoperm, and then, the 10 kV high-voltage transformer was designed and manufactured.