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Rensselaer Polytechnic Institute
Thermal Analysis of an Integrated Power
Electronics Module
MANE-6980 Tentative Project Proposal Draft
Nicholas Palumbo
10/3/2012
____________________________
Professor Ernesto Gutierrez-Miravete
Abstract
Integrated power electronics such as IGBT’s are widely used to efficiently deliver
electrical power in electrical drive systems in transportation, home electronics, and
electrical grid applications. Applying integrated power electronics to electric drive
systems is causing the need to improve volumetric requirements, ruggedness, weight,
reliability, noise levels, and thermal heat dissipation. Modern integrated power
electronics have a much higher power density compared to past technologies and
companies continue to innovate. The limiting factor in these electronic components is
heat removal. In order to achieve adequate cooling at current power densities, design
engineers are forced to look beyond standard forced-convection air cooling. Liquid
cooling has become an accepted and necessary form of heat dissipation for integrated
power electronic modules. Two notable cooling technologies that have evolved into
efficient and reliable means to dissipate heat are cold plates and heat pipes.
Introduction
Integrated power electronic modules consist of components such as insulated gate bipolar
transistors (IGBTs), rectifying diodes, snubber capacitors, direct current (DC) link
capacitors, resistors, gate driver boards and many other components based on the
application. However, IGBTs are the main source of waste heat loads. The IGBT is a
semiconductor power conversion device which can achieve a high power density while
performing its fundamental role of electrical power processing, known as switching, at
high frequencies. IGBT power losses are divided into three groups: conduction losses,
switching losses and blocking losses (which are normally disregarded). Conduction
losses deal with a series connection of DC voltage source of the on-state zero current of
the collector-emitter voltage and resistance. Switching losses deal with turn-on energy
losses in the IGBT taking into account the switch-on energy and the switch-on energy
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caused by the reverse-recovery of the free-wheeling diode; switching losses in the IGBT
are the product of switching energies and the switching frequency.
With the intent of creating a highly power dense integrated power electronic modules
cold plates have matured into a common cooling technique. Unless properly designed,
high rates of heat generation result in high operating temperatures for electronic
equipment, which then jeopardizes its safety and reliability. In order to promote the
needed heat transfer and improve temperature distribution within the power devices cold
plates must be designed with the correct attributes for efficient heat transfer and
dissipation. Cold plates act as an indirect cooling system where there is no contact
between the cooling medium and the component. The heat generated by the IGBT is
transferred from the case to the heat sink block which has imbedded piping containing a
circulating cooling medium. The heated liquid is then cooled by an external heat
exchanger. Desirable characteristics of cooling liquids include high thermal conductivity,
high specific heat, low viscosity, high surface tension, and high dielectric strength.
Required heat removal rates can be achieved by varying inlet temperature, flow rate, flow
type (laminar or turbulent), thermal contact boundaries, and materials used for both pipe
and heat sink.
There are many ways to cooling integrated power electronic modules. Cold plates have
many benefits to their implementation but there are other technologies that can
adequately compete. Making use of a heat pipe for cooling integrated power electronic
modules could be a viable alternative.
Problem Description
The limiting factor for designing integrated power electronic modules is the ability to
removal a sufficient amount of heat. The design of the cold plate must adhere to strict
requirements based on the application it is being used in. Into today’s applications of cold
plates, restrictions are placed on many attributes that affect the effectiveness of heat
dissipation. The packaging of these power dense components within the integrated power
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electronic modules impacts the capability of this technology to obtain a higher switching
frequency. A higher switching frequency is desired of these devices because it translates
directly into better power quality; however higher switching frequency results in a poor
power efficiency (increased losses in the form of heat).
Methodology / Approach
First objective is to determine the operating voltages and currents for the IGBTs within
the integrated power electronics module. Once the operating conditions are known, a
calculation must be done to determine the total losses of the integrated power electronics
module. Once losses are determined the design and analysis of a cold plate can begin.
Materials, flow rate, pressure drop and all application based inputs must be addressed
during this phase. Calculations will be completed to determine heat spreading,
effectiveness of force convection fluid cooling, and develop an understanding of
performance based attributes. Once standard calculations are complete the goal is to
perform a COMSOL Multi-physics analysis of the cold plate design to compare
calculated results and obtain a better understanding of cold plate operation. Following the
computer analysis, alternate forms of cooling will be looked into with emphasis on heat
pipes. The objective is to design a heat pipe which has a comparable ability to cool the
integrated power electronics module.
Resources Required
Based on the scope of work, the following is a list of resources required to complete the
project: SolidWorks / AutoCad Modeling Software for the design of the cold plate
models, COMSOL Multi-physics for the thermal analysis of the cold plate dissipating
heat from the IGBTs, Microsoft Office, and the Cole Library for literature resources.
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Expected Outcomes
The primary objective of this project is to design a working cold plate that can
successfully remove heat from the integrated power electronics module. In order to
design a cold plate, losses of the integrated power electronics module must be
determined. Goal is to refine the original cold plate design with hope of meeting various
requirements (i.e., ambient temperature, inlet water temperature, fluid velocity
limitations, material limitations, etc.). Following the cold plate design and analysis, goal
is to perform an analysis with COMSOL Multi-physics software to confirm and compare
the desired results of the cold plate design. Secondary objectives consist of exploring
alternate forms of cooling technologies, and developing a possible heat pipe design which
could successfully cool the integrated power electronics module.
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Milestones / Project Schedule
Week Number
Task
1
2
3
4
5
6
7
8
9
10
11
12
9/19/2012 9/26/2012 10/3/2012 10/10/2012 10/17/2012 10/24/2012 10/31/2012 11/7/2012 11/14/2012 11/21/2012 11/28/2012 12/5/2012
Research Integrated Power
Electronics Module Cooling
Techniques
Obtain COMSOL
Multiphysics & Install, Run
Tutorials
Determine System Level
Requirements
Determine Cold Plate Tubing
Concepts / Layouts
Select Flow Configurations /
Perform Pressure
Calculations
Model Cold Plate with
Thermal Loads
Perform Detailed IGBT Model
Study
Alternative Cooling Device
(Heat Pipe)
Choose Alternative Cooling
Device and Perform Study
Final Project Report
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References
Below is a list of potential technical references for this project:
1. Jamnia, Ali. Practical Guide to the Packaging of Electronics 2nd Edition. Boca Raton, FL: CRC Press Taylor 7 Francis Group, LLC., 2009. 2. G. Kandlikar, Satish and N. Hayner II, Clifford. Heat Transfer Engineering Volume 30, no 12, 2009. Liquid Cold Plates for Industrial High-­‐Power Electronic Devices – Thermal Design and Manufacturing Considerations. Taylor and Franics Group, LLC., 2009. 3. Kutz, Myer (2006). Mechanical Engineers' Handbook -­‐ Energy and Power (3rd Edition). (pp: 371-­‐418). John Wiley & Sons. Online version available at: http://www.knovel.com.colelibprxy.ewp.rpi.edu/web/portal/browse/display?_EXT_
KNOVEL_DISPLAY_bookid=1532&VerticalID=0. 4. A. Soule, Christopher. Cooling High-­‐density Electronics with Liquid-­‐cooled Cold Plates. Powertechnics Magazine, August 1988, (pp: 21-­‐27). Laconia, NH: Thermshield, LLC. 5. Valenzuela, Javier; Jasinski, Thomas; Sheikh, Zahed. Power Electronics Technology, February 2005; Liquid Cooling for High-­‐Power Electronics (pp. 50-­‐56). www.powerelectronics.com. 6. Cooling of Electronic Equipment (pp 15-­‐1 – 15-­‐69). 2005, Quark Press.http://highered.mcgrawhill.com/sites/dl/free/0073398128/835451/Chapter15
.pdf . Accessed 10/01/2012. 7. Cornell Aeronautical Laboratory. Guide Manual of Cooling Methods for Electronic Equipment. Lewis Library, NACA Cleveland, Ohio. Feb 18, 1957. http://www.dtic.mil/cgi-­‐
bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA278747 8. Shipboard Propulsion, Power Electronics and Ocean Energy. Chapter 6: Power Converter Cooling. Jan 1, 2011. Taylor and Francis, LLC. 9. J. Brennan, Patrick and J. Kroliczek, Edward. Heat Pipe Design Handbook. Towson, Maryland 21201: B & K Engineering, INC. 10. Kutz, Myer (2006). Mechanical Engineers' Handbook -­‐ Energy and Power (3rd Edition). (pp: 335-­‐361). John Wiley & Sons. Online version available at: http://www.knovel.com.colelib-­‐
prxy.ewp.rpi.edu/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=1532
&VerticalID=0. 11. Yang, Bo. Chapter 3: Integrated Power Electronics Module (pp 72-­‐93). Accessed 09/25/2012. 12. H. Lienhard IV, John and H. Lienhard V, John. A Heat Transfer Textbook, 4th Edition. Cambridge, MA: Phlogiston Press, 2012. 6