72.

D. Hansen, J. Holtz and R. Kennel, "Cutter distance sensor for an adaptive position-/torque control in cross cutters" in Conference Record of the 2002 Annual Pulp and Paper Industry Technical Conference (Cat. No.02CH37352), 2002, pp. 54--61.

Abstract:
Cross cutters are important equipment in the paper industry. A well-known design is to use mechanically coupled cutters providing synchronous motion. To improve dynamic behavior of cross cutters and to reduce maintenance effort it would be advantageous to operate the cutters by separately controlled servo drives. This idea requires very exact knowledge concerning cutter positions to ensure proper operation and to avoid any crash. This paper presents a progressive sensor measuring the distance between the cutter knives and distinguishing between knives approaching or touching each other directly on the one hand and normal cutting operation with material between the knives on the other hand. Measuring results obtained by a test example of the sensor are presented.

71.

S. Soter and S. Buchhold, "Low Voltage Converter for Feeding the Net with Fuel Cell Power" in PCIM Asia 2002, 2002.

70.

S. Soter, S. Buchhold and R. Lach, "Niederspannungswechselrichter mit hohem Wirkungsgrad" in 17. Symposium Photovoltaische Solarenergie, 2002.

69.

S. Soter and R. Lach, "Noise minimization of three-phase current machines by variation and modification of control scheme and power electronics" in PCIM Europe, 2002.

68.

M. Linke, R. Kennel and J. Holtz, "Sensorless position control of permanent magnet synchronous machines without limitation at zero speed" in IEEE 2002 28th Annual Conference of the Industrial Electronics Society. IECON 02, 2002, pp. 674-679 vol.1.

Abstract:
Sensorless position control of surface mounted permanent magnet synchronous machines (SMPMSM) still is a challenge. High performance position control at low and zero speed is only possible using anisotropic effects being considered not in the fundamental-frequency machine models, but in extended high-frequency models. This paper presents a new high-frequency injection method estimating the rotor position, which overcomes the small signal to noise ratio inherent to methods of this type published so far. This enables to track even small saliencies typical for SMPM synchronous machines. A small high-frequency voltage signal is injected into the rotor d-axis with no influence on the torque producing q-current. The demodulation of the responding high-frequency current signal is independent on machine parameters. Therefore the proposed method is independent on machine parameters and simply adaptable to different machines. As only the high frequency current has to be processed for position estimation, there is no additional hardware necessary besides that for standard drives with field oriented control.

67.

R. Roesner, J. Holtz and R. Kennel, "Cellular driver/snubber scheme for series connection of IGCTs" in 2001 IEEE 32nd Annual Power Electronics Specialists Conference (IEEE Cat. No.01CH37230), 2001, pp. 637-641 vol.2.

Abstract:
In high voltage applications of inverters, series connection of power semiconductors is a well known solution. This paper presents a progressive driver/snubber scheme producing its own supply voltage without external power supply. Besides that, voltage distribution and snubber behavior are optimized and snubber energy is regenerated to the DC link of the inverter. Measuring results obtained from a real IGCT-inverter are presented.

66.

E. P. Wiechmann, R. P. Burgos and J. Holtz, "Sequential connection and phase control of a high-current rectifier optimized for copper electrowinning applications", IEEE Transactions on Industrial Electronics, vol. 47, no. 4, pp. 734--743, 2000.

Abstract:
This paper proposes an optimized sequential control technique for copper electrowinning high-current rectifiers. The converter comprises two series-connected six-pulse double-wye rectifiers, a step-down transformer, and a tuned input filter. The six-pulse rectifiers are fed from delta and polygon primary windings with different turns ratio and phase shifted by 5/spl deg/. Under the proposed control scheme, one rectifier is kept at nominal output voltage, and the other one is phase controlled to control the load's current. The proposed strategy greatly improves the rectifier's performance, reducing its reactive power maximum demand by 62{%} compared to conventional rectifiers and, therefore, reduces the input filters power rating also by 62{%}. This is accomplished while keeping the input power factor above 0.95 throughout the whole operating range. Further, the converter's reactive power consumption presents a low varying characteristic, allowing it to use a fixed filter, even when operating from a power system not capable of withstanding large reactive power variations. Finally, it presents a harmonic current distortion comparable to conventional 12-pulse high-current rectifiers. This paper presents the design and optimization procedure of the rectifying system. A 2.5 kVA laboratory prototype was used to validate the converter model, later employed in evaluating the converter operating in a 10.5 MVA copper electrowinning facility. The results obtained confirm the advantages of the proposed converter and its control strategy.

65.

S. Soter and R. Lach, "Concept of noise minimization of three-phase current machines by variation and modification of control scheme and power electronics" in PCIM Europe, 2000.

64.

A. M. Khambadkone and J. Holtz, "Current control in overmodulation range for space vector modulation based vector controlled induction motor drives" in 2000 26th Annual Conference of the IEEE Industrial Electronics Society. IECON 2000. 2000 IEEE International Conference on Industrial Electronics, Control and Instrumentation. 21st Century Technologies, 2000, pp. 1334-1339 vol.2.

Abstract:
Overmodulation enhances the power utilization of the installed capacity of a voltage source inverter. A space vector strategy is used for constant switching frequency inverters. In order to achieve the overmodulation a modified reference signal with nonuniform angular velocity is generated using a preprocessor. Such a reference wave produces low frequency harmonics in currents. The presence of current harmonics restricts the bandwidth of the fundamental component current controller in the overmodulation range. On the other hand a high bandwidth current controller is mandatory for vector control. A compensating current control is presented to allow for high bandwidth current control in synchronous coordinates.

63.

S. Soter and S. Buchhold, "Increasing Efficiently of a Converter for Feeding the Net with Fuel Cell Power by Using Modern Electronic Components" in PCIM USA, 2000.