Institute of Electrical Engineering,Chinese Academy of Sciences
Academic actvities
 

Academic actvities


International Lecture Notice [10:30am, September 9, 2016]
  Date:2016-09-07    
 

TITLE 1: Thermal Analysis of Power Electronic and Electrical Assemblies

TITLE 2: High Breaking Capacity Fuses with Improved Cooling

Date: 10:30am, September 9, 2016.  

ADDRESSThe 703 meeting room of Building 1 

Speaker: Adrian Plesca (Gheorghe Asachi Technical University of Iasi

Abstract 1: 

Since the first power MOSFET was introduced, the use of power electronics for both industrial and commercial applications has been increasing exponentially. In fact, the high input impedance of these devices allowed a considerable simplification of the control circuits cutting off costs and dimensions of power electronics systems. Power devices may fail catastrophically if the junction temperature becomes high enough to cause thermal runaway and melting. A much lower functional limit is set by temperature increases that result in changes in device characteristics, such as forward breakover voltage or the recovery time, and failure to meet device specifications. Heat generation occurs primarily within the volume of the semiconductor pellet. This heat must be removed as efficiently as possible by some form of thermal exchange with the ambient, by the processes of conduction, convection or radiation. Thermal analysis can be performed by a variety of methods. Simulation using numerical modeling is inherently a computationally intensive process, since there are many equations to be solved iteratively. Further, a power assembly including MOS semiconductors and its heat sink has been studied from thermal point of view. The progress in computer technology enables the modelling and simulation of more and more complex structures in less time. It has therefore been the aim to develop a 3D model of a power thyristor as main component part from power semiconductor converters. Then, a PCB 3D thermal analysis using a simplified thermal model of the vias, is described. Power semiconductors still have poor overload capacities and continue to need sensitive and fast-acting protection. Hence, special fast fuses have been designed to protect them. Next, it presents a study to model the operation of fuses used to protect power semiconductors, especially in the case of transient conditions for different types of power rectifiers.

Abstract 2:

In its simplest form, the fuse consists of a piece of metal wire connected between two terminals on a suitable support; and in its complex form it is made up of a cartridge fuse link mounted in a carrier and fuse base. Modern cartridge fuse links contain fusible elements mounted in rigid housings of insulating material. The physicochemical process during the operation of fusible wires under high currents densities presents complicity and seems not to be completely known. There are presented some solutions to improve the fuse cooling on the basis of aluminum heat sinks and heat sink with fan. All solutions are analyzed from thermal point of view. For the fuse with improved cooling, an over current coefficient can be defined. In the case of fuse equipped with three same aluminum heat sinks, a thermal analysis from geometrical point of view has been done. The goal was to obtain the minimum temperature in the middle of the fuse Depending on the heat sink type and/or forced cooling, the time-current characteristics for the new situation will be translated to the right side of the time-current plane and will influence the discrimination possibilities within overload range, between fuses and/or between fuses and circuit breakers.