The demand for lightweight converters with high control performance and low acoustic noise led to an increase in switching frequencies of hard switched two-level low-voltage 3-phase converters over the last years. For high switching frequencies, converter efficiency suffers and can be kept high only by employing cost intensive switch technology such as SiC diodes or CoolMOS switches; therefore, conventional IGBT technology still prevails. In this paper, the alternative of using three-level converters for lowvoltage applications is addressed. The performance and the competitiveness of the three-level T-type converter (3LT 2 C) is analyzed in detail and underlined with a hardware prototype. The 3LT 2 C basically combines the positive aspects of the two-level converter such as low conduction losses, small part count and a simple operation principle with the advantages of the three-level converter such as low switching losses and superior output voltage quality. It is, therefore, considered to be a real alternative to two-level converters for certain low-voltage applications.

Switching devices based on wide band gap materials as SiC offer a significant performance improvement on the switch level (specific on-resistance, etc.) compared to Si devices. A well known example are SiC diodes employed for example in inverter drives with high switching frequencies. In this paper, the impact on the system level performance, i.e. efficiency, power density, etc., of industrial inverter drives and of DC-DC converter resulting with the new SiC devices is evaluated based on analytical optimisation procedures and prototype systems. There, normally-on JFETs by SiCED and normally-off JFETs by SemiSouth are considered.

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