Schematic circuit diagram of the S3L inverter. The snubber circuit is highlighted in grey.
Inverters are used for converting
DC voltage into
AC voltage. Their construction typically makes use of
power transistors and
diodes. These are operated as electronic switches. In conventional designs using "hard" switching, this gives rise to
switching losses [
de][2] which, especially for high values of the
switching frequency, cause a reduction in their
energy conversion efficiency. To improve their efficiency, high-power inverters (from about 10 kW) frequently make use of a technique referred to as a three-level design (
three-level inverter).[3]
Forming the basis of the
S3L inverter is a hard-switching three-level inverter of this kind with a
T-type topology.[4] This base design is supplemented by a snubber circuit consisting of a few passive components.[5] It prevents the occurrence of simultaneously high values of voltage and current, and hence high power dissipation values, during the switching process. All switching processes therefore take place in a "soft" manner. In this way switching losses are largely avoided. Furthermore, because the snubber circuit functions, in principle, without losses, the conversion efficiency of the inverter remains high even for high values of the switching frequency.[6][7]
^Peter R. W. Martin (editor): Applikationshandbuch IGBT- und MOSFET-Leistungsmodule. ISLE Verlag, 1998,
ISBN3-932633-24-5, Section 1.2.3 Qualitatives Schaltverhalten von MOSFET und IGBT beim harten Schalten (PDF version).
^Akira Nabae, Isao Takahashi,
Hirofumi Akagi: A New Neutral-Point-Clamped PWM Inverter. In: IEEE Transactions on Industry Applications. IA-17, No. 5, 1981, pp. 518–523, doi:10.1109/TIA.1981.4503992.
^M. Schweizer, J. W. Kolar: High efficiency drive system with 3-level T-type inverter. In: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011). 2011,
ISBN9789075815153, pp. 1–10.
^M. W. Gekeler: Soft switching three level inverter with passive snubber circuit (S3L inverter). In: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011). 2011,
ISBN9789075815153, pp. 1–10.
^Manfred W. Gekeler: Weich schaltender 3-Stufen-Pulswechselrichter mit verlustfreiem Entlastungsnetzwerk. In: International ETG Congress 2011 (ETG Technical Report 130 Part B). 2011,
ISBN978-3-8007-3376-7, pp. 264-270.
^3-Level Pulse Width Modulation Inverter with Snubber Circuit; US Patent No. US 8,462,524 B2; Date of Patent: Jun. 11, 2013; Inventor: Manfred W. Gekeler, Constance (DE); Assignee: Hochschule Konstanz, Constance (DE)