Micro Channel Cooler Performance Improvement by Insonation

The motivation for this work is the need to remove waste heat from laser diodes and high speed transistors in processes which are exponentially increasing past 1 kW/cm2 as anticipated by Moore\u27s Law. The hypothesis guiding the work is that ultrasonic insonation of micro coolers employed to dissipate these heat loads can improve heat removal. It is thought that the mechanism promoting the benefit is enhancement of the ability of the coolant to remove latent heat in two-phase operation by managing entrained bubble size near the cooler\u27s exit so as to forestall flow reduction or blockage caused by large bubbles, wedges and slugs accumulating there. Insonation experiments to prove the hypothesis have been done on several micro channel coolers in the range 4-80 kHz to quantify improvement in heat flux removal. In order to understand how insonation would produce benefit in heat removal, a research effort was undertaken to study the affect of 5-30 Pa acoustic fields on air bubbles rising in small aquariums. This involved developing a Faraday cage shielded acoustic probe, along with a force-beam calibration tool, for measuring field levels near a strongly electromagnetic-radiating ultrasonic source. Experiments were conducted on columns of pseudo monodisperse, sub-millimeter diameter air bubbles in water, and other fluids using bubble generators optimized for this purpose. A numerical analysis model based on energy balance of the acoustic work done on a bubble resulted in predicting mass transfer flux, and in quantifying bubble shrinkage and growth when irradiated on either side of its resonance. The model, and experiments show that bubble populations can be predictably altered by ultrasound. The research was concluded by identifying and quantifying micro channel cooler performance change when insonated in the range 4-80 kHz. It was discovered that 28 and 58 kHz radiation of exchangers having hydraulic diameters spanning 0.02 to 0.6 mm could produce heat flux removal improvements of 5 W/cm2 in devices normally removing less than 30 W/cm2, a factor of 17%. Peak thermal resistance improvement approaching 60 % has been observed

Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology

INE/AUTC 10.0

Industrial and Technological Applications of Power Electronics Systems

The Special Issue "Industrial and Technological Applications of Power Electronics Systems" focuses on: - new strategies of control for electric machines, including sensorless control and fault diagnosis; - existing and emerging industrial applications of GaN and SiC-based converters; - modern methods for electromagnetic compatibility. The book covers topics such as control systems, fault diagnosis, converters, inverters, and electromagnetic interference in power electronics systems. The Special Issue includes 19 scientific papers by industry experts and worldwide professors in the area of electrical engineering

Measurements, Models, Systems and Design

531 s.

NASA Tech Briefs, October 2000

Topics include: special coverage sections on CAD, CAE, and PDM, and, Composites and Plastics, and sections on electronic components and systems, software, test and measurement, mechanics, manufacturing/fabrication, physical sciences, information sciences, book and reports, and special sections of Electronics Tech Briefs and Motion Control Tech Brief

In-situ Health Monitoring Applied to High-Voltage IGBT Power Modules

PhD ThesisThis thesis addresses an important issue of identifying insulated gate bi-polar transistor (IGBT) chip failures in multichip IGBT power modules. IGBT power modules are the dominant semiconductor devices of choice in high-voltage (HV) high-power converter applications which include domestic, commercial, automotive, railway, marine, aerospace and industrial applications. Commonly available HV IGBT power modules in the market are rated at 3.3 kV, 4.5 kV and 6.5 kV. These HV IGBT modules comprise several IGBT chips connected in parallel to achieve high-current capability; hence they are also known as multichip IGBT power modules. IGBT power modules are not flawless. The increased complexity of IGBT power module construction and inhomogeneous semiconductor chips make HV power modules less reliable. IGBT chips and electrical and mechanical interface material within the modules wear out and fail due to thermal cycling, operating environment or mishandling. IGBT failures while in application have repercussions on safety and failure costs. Thus the reliability of IGBTs while in their application is crucial especially in HV applications which comprise critical and large loads. To improve the reliability, an in-situ (online) health monitoring interface for HV IGBT power modules is proposed in this thesis. Two distinct advantages of in-situ IGBT health monitoring are that it allows IGBT module replacement prior to complete failure thus reducing safety and reliability risks. The second advantage is that the interval time for IGBT maintenance work can be tailored towards the real degradation rather an obligatory fixed time interval thus reducing maintenance costs. In large power modules, it is common to have IGBT chips as well as anti-parallel diode chips within the power module. This research focusses only on the health monitoring of the IGBT chips and not the diode chips. The main reason is that IGBT chips experience higher thermal stresses compared to diodes hence IGBT chips are more susceptible to failures compared to diode chips. In practice, IGBT chip failures are accompanied by a change in junction temperature. Thus this thesis proposes the use of temperature- sensitive electrical parameters (TSEPs) for in-situ health monitoring of IGBT power modules. Following a comparison of twelve traditional online TSEPs from literature and five new TSEPs proposed in this thesis, this thesis employs a novel TSEP, gate-emitter prethreshold voltage (VGE(pre-th)) as a health-sensitive parameter (HSP) for chip failure detection in multichip HV IGBT power modules. A VGE(pre-th) online chip loss monitoring circuit has been successfully implemented on a commercially available IGBT gate driver. VGE(pre-th) is measured at a fixed pre-determined instant of the gateemitter voltage (VGE) between the VGE zero-crossing (VGE(0)) and threshold voltage (VGE(th)) during IGBT turn-on. VGE(pre-th) requires low hardware with only a voltage sensor and a counter. Since it is based on the low-voltage (LV) gate side rather than the HV collector side of IGBT, VGE(pre-th) does not require HV isolation or HV insulation. Simulation and experimentation of 16-chip 3.3kV 800A DIM800NSM33-F IGBT power modules from Dynex Semiconductor Limited (Ltd) have shown that VGE(pre-th) has a good accuracy and repeatability; a linear sensitivity of 500 mV/chip loss with IGBT chip failures; a linear virtual junction temperature (Tvj) sensitivity of -2.2 mV/°C and tracks the highest chip temperature. It has thus been concluded that VGE(pre-th) can be used for both Tvj and IGBT chip failure monitoring in HV IGBT power modules. VGE(pre-th) can be tested during normal IGBT turn-on operation or during the off-state of the IGBT. In both cases the same information about temperature and loss of chip number can be detected which makes VGE(pre-th) more versatile than any other TSEP or HSP.Engineering and Physical Sciences Research Council (EPSRC), Newcastle University

Design/cost tradeoff studies. Earth Observatory Satellite system definition study (EOS)

The results of design/cost tradeoff studies conducted during the Earth Observatory Satellite system definition studies are presented. The studies are concerned with the definition of a basic modular spacecraft capable of supporting a variety of operational and/or research and development missions, with the deployment either by conventional launch vehicles or by means of the space shuttle. The three levels investigated during the study are: (1) subsystem tradeoffs, (2) spacecraft tradeoffs, and (3) system tradeoffs. The range of requirements which the modular concept must span is discussed. The mechanical, thermal, power, data and electromagnetic compatibility aspects of modularity are analyzed. Other data are provided for the observatory design concept, the payloads, integration and test, the ground support equipment, and ground data management systems

Electromagnetic Interference and Compatibility

Recent progress in the fields of Electrical and Electronic Engineering has created new application scenarios and new Electromagnetic Compatibility (EMC) challenges, along with novel tools and methodologies to address them. This volume, which collects the contributions published in the “Electromagnetic Interference and Compatibility” Special Issue of MDPI Electronics, provides a vivid picture of current research trends and new developments in the rapidly evolving, broad area of EMC, including contributions on EMC issues in digital communications, power electronics, and analog integrated circuits and sensors, along with signal and power integrity and electromagnetic interference (EMI) suppression properties of materials