Comparative Evaluation of Gate Driver and LC-Filter Based dv/dt-Limitation for SiC-Based Motor-Integrated Variable Speed Drive Inverters
Michael Haider, Pascal S. Niklaus, Manuel Madlener, Gwendolin Rohner, Johann W. Kolar
Abstract
Compared to state-of-the-art IGBTs, SiC power semiconductors allow to achieve ever higher system efficiencies and higher power densities in next-generation Variable Speed Drives (VSDs), thanks to their smaller relative chip size, ohmic on-state characteristic and lower specific switching losses resulting in a smaller switching-stage footprint and lower heat sink as well as DC-link capacitor volumes. However, the high slew rate of the switching transitions, an inherent consequence of the low switching losses, represents a major challenge and potentially results in lifetime degrading unequal voltage distribution across the motor windings and bearing currents. This work analytically and experimentally compares different means for d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$v$</tex-math></inline-formula> /d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t$</tex-math></inline-formula> -limitation, namely, a conventional passive LC-d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$v$</tex-math></inline-formula> /d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t$</tex-math></inline-formula> -filter and a Gate Driver (GD)-based approach based on increased GD resistances in combination with explicit Miller capacitors, at the example of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text {10}$</tex-math></inline-formula> kW industrial motor-integrated VSD. For a state-of-the-art d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$v$</tex-math></inline-formula> /d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t$</tex-math></inline-formula> -limitation of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text {6}$</tex-math></inline-formula> V/ns the LC-filter shows lower losses compared to the GD-based limitation. The latter, however, has a higher part-load efficiency and/or lower losses compared to the (roughly) load independent losses in the LC-filter resulting from the dissipation of the energy stored in the filter capacitor within each switching cycle, beneficial for light loads, e.g., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${< 40}\,$</tex-math></inline-formula> % of rated output power. Next-generation motors with reinforced insulation allow a d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$v$</tex-math></inline-formula> /d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t$</tex-math></inline-formula> -limitation of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text {15}$</tex-math></inline-formula> V/ns. In this case, the GD-based limitation shows lower losses in the whole operating range, since they directly scale with the now smaller overlap of voltage and current resulting from the faster switching transitions. Considering a state-of-the-art motor, finally, a hardware demonstrator of a three-phase VSD employing an LC-filter to limit the d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$v$</tex-math></inline-formula> /d <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text {5.6}$</tex-math></inline-formula> V/ns is realized, which achieves a full inverter stage power density of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text {30}$</tex-math></inline-formula> kW/dm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{3}$</tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text {497}$</tex-math></inline-formula> W/in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\text {3}$</tex-math></inline-formula> ) and an inverter efficiency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$>\! \text{99}\,$</tex-math></inline-formula> %.