The paper discusses the application of the current-source concept in the gate drivers for silicon carbide transistors. There is a common expectation that all SiC devices will be switched very fast in order to reach very low values of switching energies. This may be achieved with the use of suitable gate drivers and one of possibilities is a solution with the current source. The basic idea is to store energy in magnetic field of a small inductor and then release it to generate the current peak of the gate current. The paper describes principles of the current-source driver as well as various aspects of practical implementation. Then, the switching performance of the driven SiC transistors is illustrated by double-pulse test results of the normally-ON and normally-OFF JFETs. Other issues such as problem of the drain-gate capacitance and power consumption are also discussed on the base of experimental results. All presented results show that the currentsource concept is an interesting option to fast and efficient driving of SiC transistors.

The positive asymptotically stable continuous-time linear systems are approximated by corresponding asymptotically stable discrete-time linear systems. Two methods of the approximation are presented and the comparison of the methods is addressed. The considerations are illustrated by three numerical examples and an example of positive electrical circuit.

The paper describes a prototype operator panel, which was designed to operate with the S7-200 family of Programmable Logic Controllers (PLC-s) from Siemens. Most of the functionality of the operator panel was implemented in a computer program, which runs on a PC-class computer. The program communicates with a PLC through its communication port configured in the Freeport mode. Two kinds of interface between the PC, and the PLC are supported: wired, and wireless. For wired connection a standard PC/PPI cable supplied by Siemens is used. For wireless connection two communication modules were designed, which operate in the free 433 MHz band. The operator panel program is intuitive, and easy to use. States of PLC inputs and outputs are presented using graphical objects. It is possible to modify states of the outputs, and monitor and edit any variable in the M and V memory in the PLC. The application supports also alarming. The program can be run on any computer with the MS Windows operating system installed. This makes the solution very cost-effective. Providing both wired and wireless communication radically increases flexibility of the proposed solution. The panel can be quickly mounted in areas, where pulling new cables is inconvenient, difficult or expensive.

The paper presents the results of research work on the development of a rapidprototyping test stand for testing: servo control algorithms, trajectory generation, algorithms for increasing overall quality of the feed-drive modules within two axis (X-Y) table of the milling machine. Open architecture interface of the prepared control system lets the potential user test functionality of integration of diagnostic tools within the motion controller - directly, without taking into account communication with top-level CNC system.

A microgrid with parallel structure operating under islanded mode is considered in this paper. Under microgrid islanded operation mode, lines bring adverse effect for power distribution between microsources (MSs). Because traditional droop control ignores this effect, MSs adopting this method can not achieve satisfactory power distribution. A kind of droop control including line compensation applied to this microgrid is proposed. It can eliminate this effect to obtain satisfactory power distribution. The relationship of two kinds of droop control with power distribution is analyzed. The reference voltage generated by droop control is applied to control output voltage of MSs. Comparison of two kinds of droop control through MATLAB/Simulink simulation is made to verify the superiority of droop control including line compensation for power distribution. The relationship between PCC voltage and output power of MSs is also presented.

This paper presents an analysis of the stator teeth geometry impact on the parameters of the 8-pole radial magnetic bearing. In this paper, such parameters as current gain and position stiffness have been analysed. Additionally, we have proposed criteria for evaluating the characteristics of these parameters by calculating the variability of current gain and position stiffness. The research has been performed by solving the magnetic bearing actuator boundary problem using the finite element method. Magnetic force has been calculated using the Maxwell stress tensor method. Other parameters, such as current gain and position stiffness have been calculated as partial derivate of the force with respect to control current and position of the rotor.

The paper presents the problem of sensorless control of a permanent magnets synchronous motor (PMSM) without a damping cage for fan applications. Frequency control was used according to the principle of v/f = const. In order to reduce the power consumption of the drive system, the optimal voltage to the motor frequency characteristics was tested in the laboratory. The experimental studies was performed on a laboratory set of a drive consisting of two coupled PMSM machines, where one machine was supplied by a transistor inverter and the other was a passive load. A new criterion based on minimizing the module of stator current vector was proposed and an optimization algorithm in steady states was tested. The results of laboratory tests confirmed the validity of the applied solution for the fan drive.

In this paper a comparison of numerically determined and measured electromagnetically exited noise of an induction motor is presented. The calculations are accomplished using FEM for an example motor, which is a 290 kW inverter-fed asynchronous machine. The approach starts with the electromagnetic and mechanical consideration. The focus is set on acoustic considerations, which contain the 3D-FE-model and measurement setup in the sound chamber.

In the paper issues related to the design of a robust adaptive fuzzy estimator for a drive system with a flexible joint is presented. The proposed estimator ensures variable Kalman gain (based on the Mahalanobis distance) as well as the estimation of the system parameters (based on the fuzzy system). The obtained value of the time constant of the load machine is used to change the values in the system state matrix and to retune the parameters of the state controller. The proposed control structure (fuzzy Kalman filter and adaptive state controller) is investigated in simulation and experimental tests.

The paper presents the mathematical model of an autonomous induction generator with the AC load circuit and the converter control system of the voltage magnitude at the terminals of stator generator. The control algorithm and the structure of the control system are described. The simulation results of the control system are presented and discussed.

In this paper the design and the magneto-static simulation of axial-flux permanent- magnet stepper motor with the disc type rotor is presented. Disk motors are particularly suitable for electrical vehicles, robots, valve control, pumps, centrifuges, fans, machine tools and manufacturing. The brushless machine with axial flux and permanent magnets, also called the disc-type machine, is an interesting alternative to its cylindrical radial flux counterpart due to the disk shape, compact construction and high torque density. This paper describes a design of four phase microstepping motor with the disc type rotor. The FEM modeling and the 3D magneto-static simulation of the disk stepper motor with permanent magnets is being subject of the article, too. Disc rotor type permanent magnet stepper motor for high torque to inertia ratio is ideal for robotics and CNC machines.

The paper deals with construction of single-phase line start permanent magnet synchronous motor. Circuit-field single-phase line start permanent magnet synchronous motor model based on the mass production single-phase induction motor was applied in Maxwell program. Various rotor constructions were taken into account. Influence of the rotor construction on the motor properties was examined. Running motor performances were examined.

The presented paper concerns a novel concept of hybrid piezoelectric motor based on electroactive lubrication principle. Its structure is combined of quasi-static and resonance piezoelectric actuators, synchronizing their work to generate the rotary movement. The hybrid motor topology is compared to the existing piezoelectric motors, regarding its field of applications in embedded systems with very high security requirements. The electroactive lubrication principle is briefly presented with regards to optimization of the hybrid motor. The performance principle of the hybrid motor is described in terms of its working cycle. The assembling process of the prototype hybrid motor is briefly explained with emphasis put on the frequency and impedance tuning of the applied quasi-static and resonance piezoelectric actuators. Next, the hybrid motor power supply system is described and chosen measured performance characteristics are presented. Finally, conclusions concerning the features of the tested prototype hybrid motor and possible solutions of the faced issues, during assembling and testing, are presented.