 |
 |
EPE Journal Volume 15-4 - Papers
- Influence of repetitions of short-circuit conditions on IGBT lifetime
- Challenges in Using the Latest Generation of IGBTs in Traction Converters
- A Non-Dissipative Reflex Charging Circuit
- Transient and Steady States Thermal Analysis and Simulation of Asynchronous Machine at No-Load Condition
- Suppressing Low Frequency Resonance Oscillations of a Two-Mass System by Active Damping
- Behavior of Synchronous Machines Subjected to Voltage Sags of Type A, B and E
- Basic Operation Principles and Electrical Conversion Systems of Wind Turbines
EPE Journal Volume 15-4 - Editorial
By B. Sneyers
The editorial of EPE Journal volume 15-4, October - December 2005, "EPE 2005, Dresden, where university meets industry", written by Ir. Brigitte Sneyers, Secretary General of EPE Association.
EPE Journal Volume 15-4 - Papers
By F. Saint-Eve, S. Lefebvre, Z. Khatir
The paper deals with the behaviour of PT and NPT IGBTs under repetitive short-circuit operations. The repetition of these severe working conditions is responsible for one mode of devices ageing and results unavoidably in the components failures. A long term campaign of experimental tests was made in order to determine the number of short-circuit operations these devices can support before failure for different dissipated energies during the short-circuit tests. The results show the very good ability of these devices to work in short-circuit operations when the dissipated energy is lower than a particular critical energy. Depending on the dissipated energy level, different failures modes can appear, in both PT and NPT transistors. In addition, a 1-D numerical simulation was realised in order to estimate the internal temperature in the silicon chip when the failure occurs.
By M. M. Bakran, H.-G. Eckel, M. Helsper, A. Nagel
The voltage class 6.5kV was the last step to now cover completely the whole range of voltages for traction starting with 1.7kV and 3.3kV. This lead to the general introduction of the IGBT across the whole power range of traction. In first IGBT generations the Non Punch Through design dominated here. The latest generation of IGBTs feature characteristics like field-stop design or trench design. Thus high cosmic ray withstand capability can be combined with low VCesat. For the high-power high-voltage application as used in traction, the introduction of the field stop leads to a significant change in the switching behavior compared to the conventional NPT-design. It will be shown how the IGBT and diode turn-off characteristics change and how sensitive it is to parasitic circuit characteristics. Especially in high-power circuits with relatively large stray inductances, this is a device and application challenge. Further more it will be shown that the IGBT overvoltage during turn-off transients can be controlled only by using a highly dynamic gate driver. Since no active control of the diode turn-off is possible, the peak-voltage must be limited by appropriate circuit and device design. For new generations of IGBT and diode, this behavior should be considered carefully by the semiconductor development.
By Y. C. Hsieh, C. S. Moo, C. K. Wu, J. C. Cheng
A novel circuit is proposed to implement Reflex charging for rechargeable batteries. The required asymmetrical bilateral pulses for Reflex charging are generated controlling the only one active power switch with pulse-width-modulation (PWM) control. The pulse width of the charging current is regulated simply by controlling the duty ratio of the active power switch, while the amplitude and duration of the negative impulse can be determined by the designed circuit parameters. Experimental tests are carried out to verify the theoretical analyses.
By O. I.Okoro, B. Weidemann
In this paper the thermal analysis and simulation of a squirrel-cage Asynchronous machine are presented. The algebraic and differential system of equations governing the steady and transient states thermal behaviour of the machine respectively are first represented in state variable form with temperature rise as state vectors and thereafter solved numerically with the help of commercially available software package, MATLAB©. It is observed that the computed average temperatures of the machine parts at no-load compare satisfactorily well with the experimental results.
By D. Alders, R. Kennel, J. O. Krah, J. Quan
Mechanical couplings between electrical motors and mechanical loads or processes usually provide rather low stiffnesses. This situation often results in resonance problems due to the interdependencies between the inertias of motors and loads coupled by elastic couplings. This paper describes the possibility of suppressing low frequency resonance oscillations by an active method instead of mechanical damping equipment. A special filter is integrated into the drive control loop. This paper shows the optimisation of the filter parameters to obtain good damping of the mechanical system.
By F. Carlsson, C. Sadarangani
Voltage sags and voltage interruptions are huge power quality problems for many industries. Voltage sags cause apart from eventual tripping, large torque peaks, which may cause damage to the shaft or equipment connected to the shaft. This paper illustrates how the stator flux in a synchronous machine changes during voltage sags. These changes result in torque peaks. An analytical time dependent expression of the stator flux during voltage sags explains the behaviour of synchronous machines and why there are high torque and current peaks during voltage sags. Simulations verify the expressions, and illustrate the dependence of torque and current peaks on voltage sag duration and magnitude.
By H. Polinder, S.W.H. de Haan, M. R. Dubois, J. G. Slootweg
This paper gives an overview of electrical conversion systems for wind turbines. First, the basics of wind energy conversion with wind turbines are reviewed and requirements with respect to the electric system are considered. Next, the three classical conversion systems are described with their strengths and weaknesses: constant speed, variable speed with doubly-fed induction generator and variable speed with direct-drive generator. The applied power electronic converters are shortly addressed. Finally, alternative generator systems and trends are discussed. There is a clear trend towards variable speed systems. Doubly-fed induction generator systems are increasingly equipped with grid fault ride through capabilities. For direct-drive turbines, the radial flux permanent-magnet synchronous generator is cheaper and more efficient than the electrically excited synchronous generator. It is expected that the voltage level of generators will increase up to values in the order of 5 kV.