Publikationen

The Resonant Commutated Twin Pole Inverter (RCTPI), a novel resonant pole inverter topology using only main switches, is introduced. One phase of a voltage source RCTPI consists of four switches arranged in two symmetric half-bridges called the twin poles. Each pole carries half of the phase current. The switches are turned off as zero voltage switch (ZVS) and zero current switch (ZCS) respectively and turned on under ZCS both. Switching losses in the semiconductor devices can be reduced in all operating points by soft switching, while overall losses are reduced only at high load currents. The concept can be realised using IGBTs in standard packages. Single switch modules, half- and full-bridge modules and some six-packs are suitable – this is an advantage compared to many other resonant topologies.

To reduce the losses of power inverters, resonant topologies replace hard switching power inverters. This paper shows the first investigations and measurements carried out to design a three phase current link power inverter in ARCP (Auxiliary Resonant Commutated Pole) topology as well as the finally measurements and results achieved with the complete system.

SiC-JFETs are promising for many future applications but have a normally-on behaviour, which usually necessitates an auxiliary MOSFET to achieve self-blocking capability. However this characteristic is predestinated to current source inverter topologies as an attractive alternative for fast switching applications. The paper presents practical investigations o SiC-JFETs with a modified driver stage in a current source inverter and for comparison in a voltage source inverter topology. Measurement results of both topologies at a frequency of 250 kHz are included. Furthermore differences in the minimising of switching losses for each topology are shown.

Synchronous machines with air-gap permanent magnet excitation are advantageous in many modern applications. As a result of the construction principle the stator inductivities are often very low. Therefore, common voltage source inverters with sinusoidal output currents are not automatically the best supply solution for these machines. Either load reactors have to be used to smooth the output current or the high du/dt-rates of faster switches produce EMI problems and overvoltages at the machine windings. Investigations have shown that sine-wave machine currents are not the most effective way to feed these drives. This paper presents a novel way to overcome these problems by using a current source IGBT-inverter. The investigated system consists of a pulse-rectifier, a DC-current-link and an inverter with an output capacitor bank to decouple the stator currents from the DC-link. A simple, modular inverter construction is proposed. It makes no use of snubbers and is scalable over a wide power range. Practical experiments to prove the feasibility have been carried out with positive results.

Zero Voltage Switching (ZVS) as applied in the Auxiliary Resonant Commutated Pole Inverter (ARCPI) can reduce drastically the relatively high switching losses of High Voltage IGBT-Modules. Thus the switching frequency can be much higher than in conventional hard switched converters. This paper describes the construction of a scaleable ARCPI-structure. The structure was tested successfully at first in an 80 kVA inverter test-setup, while this paper presents first measurements and experiences with an 1 MVA test-setup with 3.3 kV-IGBTs. Switching frequencies up to 5 kHz were achieved with a rated load current of 800 ARMS.

This paper illustrates the development of an ARCPI with a simple, fully digital control which works on the basis of pre-calculated switching time values stored in a look-up table of a PLD. Although the load current is the only measured input value of the control system there is no need for special driver-stages with a zero-voltage detection possibility. The PLD-control can be easily adjusted to cope with different input parameters and therefore it can be used in full power range without hardware changes. The paper presents the calculation models for the values of the resonant components and the switching times and compares the theoretical results whith the measurements carried out on two different test-setups in the mid and high power range.