Jan Knobloch

Implementation of diagnostics functions in the IGBT drivers, part 1. — Diagnostics

The paper deals with possibilities of power IGBT transistor diagnostics directly in driver of voltage source inverters. It is necessary to implement the diagnostics circuits as close as possible to the power IGBT transistor due to high demands on drive reliability and failure predictability in many applications.

Implementation of diagnostics functions in the IGBT drivers, part 2. — HW implementation

Diagnostics methods of power inverters are usually based on using measurements of feedback electric quantities. This paper proposes ways of direct diagnostics of power semiconductors parts in its drivers. In the first part of the article, there were proposed and described methods of direct power semiconductors diagnostics for usage in voltage source inverters. Circuits for the diagnosis are assumed in power transistor driver. This paper will focus on hardware requirements, which flows from proposed solution, especially on microcontroller, control units and data collection form IGBT drivers. The description of hardware solutions for measurement of diagnostics quantities is introduced in the first part of the paper.

Intelligent IGBT driver concept for three-phase electric drive diagnostics

This document focuses on the problem of diagnostics of an electrical drive equipped with a voltage source inverter (VSI). The attention is concentrated on a hardware design for a power system diagnostics. A new concept of a power transistor driver is proposed. This concept of the driver integrates functions for monitoring of a large number of electrical drive parameters which are transferred to the superior control system for an actual operation state evaluation or an eventual failure state detection. The proposed solution introduces the possibility of an internal electrical quantities feedback realization (phase currents and DC link voltage) directly in the drivers of power transistors without using standard current and voltage sensors. The feed-backs can be extended with output voltages measurement of the inverter which can be further used in online identification of motor parameters for a model of the electrical drive. This model can be used for a control technique adaptation (with respect to maximal efficiency, maximal dynamic performance or also for sensor-less speed control or position control).

Measurement of Power Transistors Dynamic Parameters

This article deals with analysis of switching processes of power transistor as well as with description of performed measurement methods of these dynamic processes. The results are demonstrated on power IGBT transistor, nevertheless the measurement methods are valid for all power devices in general. Due to the fact, that the extremely dynamic and power processes have to be analyzed, then the special measuring laboratory workplace (MLW) was developed for proper oscillographic measurement of these processes. Further, the current sensor with ultra-wide bandwidth has to be developed. Description of the MLW is presented in this paper together with its development process. This paper gives the complex methodology for analysis of power devices switching processes.

Dynamic Model of Wye Connected Induction Machine

The paper deals with a derivation of a dynamic model of induction machines with wye connected stator and rotor windings. The mathematical modeling of any electric machine is an inseparable part of the knowledge of any future/present engineers involved in the control of the electric drives. In the paper, several models of the induction machines are derived in a comprehensible way with an emphasis on structural and parameter integrity of all models. Derived dynamic model with line-to-line stator voltages presents a simple substitution to more general but also more complicated natural model of induction machines.

Measurement of High-Frequency Currents in Power Electronics

The paper briefly presents the possibilities of sensing the high frequency collector current of the power transistor. Subsequently, attention is paid to the current transformer as a promising sensor. The transformer is compared to a professional current probe. Subsequently, its analysis is done by finite element method, experimental verification of calculation and analytical explanation. All this leads to a current transformer being suitable for the purpose. Finally, there is a practical demonstration of its function.

Test stand for obtaining power transistors switching characteristics during aging

This paper aims to construction, control and implemented measurement method of laboratory stand in order to acquire insulated gate bipolar transistor transients. The transients waveforms are consequently used to obtain indicators of the transistor age. The lifetime tests of an insulated gate bipolar transistor are introduced. Consequently, a novel architecture of measuring stand in order to provide lifetime tests is designed. Also the control algorithm is presented. A fundamental part of this work is a method of measuring switching waveforms including a high frequency current. Acquired waveforms of transistor switching are presented. Finally, the trend of chosen aging indicator values was obtained from the acquired data. Namely the influence of aging on turn-off time was observed.

Two-switch forward converter efficiency optimization

This contribution presents a mathematical tool for analytical calculation of the optimum switching frequency and transformer parameters of a switching power supply utilizing a two-switch forward converter. The calculations are based on minimization of total power loss of the converter with given switching semiconductors and size of transformer and inductor core. This allows the designer to construct a converter with greatest efficiency using given parts (keeping cost of the components). The results are power saving, less waste heat and possibly smaller size and weight of the converter or power supply. Applications include photovoltaic inverter, electric vehicle charging, industrial power supply and any isolated DC/DC converter in general.

Measurement and evaluation of DC motor starting torque

The paper deals with the measurement and evaluation of starting torque of a DC motor. The torque is estimated from an actual motor speed during starting with the Kalman filter. The actual speed is measured with an incremental rotary encoder. The main aim of this paper is a determination of correct setting of all parameters in Kalman recursive algorithm from the perspective of very good coincident of estimated torque and actual torque calculated based on the mechanical equation of this machine. All theoretical results are confirmed by experiments.

Modular system of converters with interleaved structure

This article deals with modular system of DC-DC converters which contains more than one converter. It is possible to connect all converters in parallel for gain high output current, all converters in serial for high output voltage or various combinations to reach desired output voltage and current. The paper describes possible control structures for mentioned connections. This system is self-reconfigurable - whole system should immediately change internal connection according required output parameters. The forward converter with a transformer was chosen as a basic element of the system. The modular system is interleaved; it leads to output current and voltage ripple reduction and cheaper output filter.