No description available.

Twist plays an important role in textile technology, particularly in the production of staple yarn structures. Due to the higher yarn quality and flexibility of the process, most short staple fiber yarns are produced in the ring spinning process in comparison to other high-speed spinning processes, such as rotor or air jet spinning. To impart twist in the yarn, the ring/traveler system, rotor and air jet nozzle are used in the ring, rotor and air jet spinning processes respectively. However, the productivity of the ring spinning process is limited significantly due to the frictional heat generated between the ring and traveler, especially at higher angular spindle speeds, which is crucial for the spinning of man-made fibers. This paper aims to describe the recent developments and solutions for increasing productivity in the ring spinning process in a systemic way. To reduce the friction, different topologies and surface modifications in the ring/traveler system were made to increase the angular spindle speed of maximum 23,000 rpm. To eliminate the friction, the twisting element was made of an air bearing or magnetically elevated rings were developed by replacing the ring/traveler system completely, thus permitting a higher angular spindle speed of up to 50,000 rpm. Further approaches deal with cap, loop and nova spinning or Nu-Torque technology to reduce yarn tension or residual torque in the yarn, respectively. The results of the presented work reveal the potential of different developments, especially in the field of twisting system, so that the productivity of ring spinning can be increased drastically.

No description available.

This work is focused on innovative construction of the industrial radial sealless pump and mainly on construction of the three phase DC/AC converter based on new semiconductor technology SiC. These new semiconductor devices allow move switching frequency up to 100 kHz. For such high switching frequency new non-conventional topology of the output filter was designed. This high frequency is currently unusual in three-phase application with output voltage 400V. High switching frequency reduces size of wound components of the output filter and its presence is accepted in terms of total weight and price of the whole system. Clear sinus waveform of the output converter voltage reduces torque ripple, EMC and extend the lifetime and reliability of mechanical parts and the whole pump drive. Three phase synchronous motor is directly placed into the pump body and is designed as slotless motor. In the inlet area is the classical bearing replaced by active magnetic bearing. It is used due to possibility to pump aggressive liquids or substances where high level of cleanness has to be guaranteed.

Twist plays an important role to impart tensile strength in yarn during the spinning process. In the most widely used ring-spinning machine for short staple yarn production, a combination of ring and traveler is used for inserting twist and winding the yarn on cops. The main limitation of this twisting mechanism is the friction between the ring and traveler, which generates heat at higher speed and limits the productivity. This limitation can be overcome by the implementation of a magnetic bearing system based on superconducting technology, which replaces completely the existing ring/traveler system of the ring-spinning machine. This superconducting magnet bearing consists of a circular superconductor and permanent magnet ring. After cooling the superconductor below its transition temperature, the permanent magnet ring levitates and is free to rotate above the superconductor ring according to the principles of superconducting levitation and pinning. Thus the superconducting magnetic bearing (SMB) ensures a friction-free operation during spinning and allows one to increase spindle speed and productivity drastically. The yarn properties using the SMB system have also been investigated and they remain nearly identical to those of conventional ring yarns.