Josef Cernohorsky

Detailed measurement and simulation of FeNdB permanent magnet used for magnetic spring

The ring shaped rare earth permanent magnets are tested in conditions corresponding to the magnetic spring, where two magnets acts in repulsive direction. The mathematical model based on the surface bounded currents was used for calculation of external field and spring forces. The magnet polarization uniformity was measured from external flux density close to magnet surface. The measurement was designed to distinguish the experimental errors from the magnet polarization errors. The agreement between experiment and model was good in all cases. The flux density scatter on the concentric circle close to magnet surface vary from 3.2 to 12.8 % on one magnet sample and the average value vary about 14 % between samples. The crank mechanism was used to simulate the magnet aging in a real condition of the magnetic spring. The repulsive force was periodically monitored during more than 120 millions of spring cycles. The observed force decrease was 2 % at the spring working point at a distance of 1 mm.

Measurement of switched reluctance motor parameters

Torque ripple presents the main disadvantage of switched reluctance motor. Advanced control methods allow to minimize the torque ripple, which requires knowing the motor parameters — inductance and torque characteristics. The paper presents parameter identification of switched reluctance motor with 2p1/2p2 = 12/8 number of poles. Included in this document are results of inductance and torque measurements. Industrial components were used to measure torque characteristics. Characteristics are compared with finite element analysis model.

Remote measurement in electrical engineering laboratories power measurement in electrical drive system, synchronization of stepper motors

The remote access and diagnostics are very common in modern industrial system. Some of them use own proper system, some others use public standards, web based visualization or virtual network computing VNC. On Technical university of Liberec we would like to enhance education in combined, distant study form. The most of the students are experienced people which would like to increase their knowledge in their field of interest or enhance the knowledge in wider range. The main idea for education of those people is usage of programmable logical controller to handle the laboratory task and allow them to do the measurement remotely by their own. In the paper there are several examples how to create or modify laboratory tasks in this way.