Jiri Fort

The study of using the traction drive topology with the middle-frequency transformer

This paper presents research motivated by industrial demand for special traction drive topology devoted to minimization of traction transformer weight of traction vehicles. The main attention has been given to the special traction drive topology for AC power systems: input high voltage trolley converter (single phase) - middle frequency transformer (single phase) - output converter (single phase voltage-source active rectifier + three phase voltage-source inverter) - traction motor. This configuration can minimize traction transformer weight against topology with classical 50 Hz traction transformer. Several variants of innovative topologies of the traction vehicles fulfill the weight reduce requirements have been presented.

The torque ripple reduction at the drive with the switched reluctance motor

The torque ripple has an adverse impact on the life of the machine and other drive components (especially bearings, gearboxes, couplings, etc.) and also produces an unpleasant acoustic noise. The reduction of the torque ripple can be solved in several ways - to select different configurations of SRM (to increase the number of phases or use the machine with higher number of steps), a suitable choice of commutation angles (so that they mutually overlap) or minimize the torque ripple by torque regulator or by direct torque control. This paper summarizes the practical results.

Ensuring the operation of electrical equipment during short-time voltage sags or power outage

This paper describes the situation of a modern electric drive (induction machine supplied from indirect frequency converter with voltage source inverter) in industry (paper mills, etc.), where a voltage sag can bring significant problems with long-time interruption of the production process. One method of operation is a direct increase of voltage in the DC-link of a frequency converter with a step-up converter during voltage sag. A transistor designed for braking is often used. It is used often present transistor designed for braking. The article presents the waveforms of voltages and currents in the circuit of an indirect frequency converter in the case of voltage sags without the intervention of a step-up converter. Then it presents waveforms with the use of a boost converter and its various control options.

The electric drive with indirect frequency converter and asynchronous motors with improved immunity against the supply voltage dips

This paper solves problematic of immunity against the voltage dips, of the power supply of the electric drive with induction motor supplied from the indirect frequency converter. There are demonstrated the several variants of adaptation of power circuits for achieving a higher immunity against the voltage dips of the power supply. First variant is using of the additional converter in DC-link. Second variant is using of the additional input converter. Third variant is using of active rectifier in place of common used non-controlled rectifier. The paper shows the results of measurement of first variant on laboratory.

AC-machine with frequency converter with immunity to voltage dips

This paper solves problematic of supply voltage dips and their influence to modern electric drive (i.e. induction machine supplied from indirect frequency converter). The paper presents the control algorithms for basic variant the most used drives (with non-controlled rectifier and without additional converter) and variants with more complicated power circuits (with active rectifier respectively with special additional step-up boost converter in DC-link).

Design of special DC-source with minimizing of its negative impact to the supply network

This paper describes the problems of design of special high power DC current source 110V/1kA. Focus was placed on the issue of minimizing the negative impact of this power source on low-frequency disturbance in power supply network.

Endurance test of the pantographs for main line vehicles

The pantographs producer needs to perform the lifetime test of the pantographs. This test usually takes 2 months when the test is running continuously 24 hours per day. We must design and build mechanical frame and control unit as well. It was our first experience with the lifetime test of this type. In addition, all preparation must be done during 2 weeks. The fast starting of the endurance test - it was our benefit before the rival company.