Thermal Engineering of Power

Thermal engineering of power electronic systems

is a key to achieve high performance and

reliability. In the focus of the new ECPE tutorial is

the thermal simulation and verification of the

SEMIKUBE IGBT converter which is equipped

with thermal sensors for verification.

Part 1: At first the topology of the IGBT converter

and it’s components are described as well as the

data sheet. Then the results of the electrical

simulation are presented in regard to

performance and thermal losses. The following

sections deal with basics of heat conduction,

convection and exchange. Practical examples

will be used for a good understanding of cooling

the hot parts in the system. After an introduction

to analytical and FEM methods five groups are

formed to exercise thermal simulations and

measurements.

Part 2: After a detailed description of the results

of the first part the impact of thermal behavior of

the converter on the reliability is discussed in

detail. The knowledge of functional requirements,

mission profiles, physics of failure, thermal

measurements (thermal images and impedance)

are needed for building-in reliability and for the

robustness validation process.

Sample Output (Heating) in computer software of thermo

# Time Array

ARTIME(17)= 0.0,4.730820e+002,9.461640e+002,1.419250e+003

1.764227e+003,1.767633e+003,1.892330e+003,2.365410e+003

2.838490e+003,3.311570e+003,3.784650e+003,3.909347e+003

3.912753e+003,4.257740e+003,4.730820e+003,5.203900e+003

5.676980e+003;

#

# solar albedo planetshine - MAIN.1 Area = 0.500000 Avg = 112.887535 31.783997 48.570499

ARSAMAIN1(17)=4.880749e+002,4.282346e+002,2.696814e+002,5.125848e+001

1.733135e+002,4.857050e+001,4.857050e+001,4.857050e+001

4.857050e+001,4.857050e+001,4.857050e+001,4.857050e+001

1.734149e+002,5.122900e+001,2.669101e+002,4.294877e+002

4.880749e+002;

#

# solar albedo planetshine - MAIN.2 Area = 0.500000 Avg = 113.716866 31.922405 47.252102

ARSAMAIN2(17)=4.929644e+002,4.238430e+002,2.660976e+002,4.994052e+001

1.747323e+002,4.725210e+001,4.725210e+001,4.725210e+001

4.725210e+001,4.725210e+001,4.725210e+001,4.725210e+001

1.762022e+002,5.012827e+001,2.717307e+002,4.300657e+002

4.929644e+002;

Joule,s Law

It state "The change of internal energy of a perfect gas is directly proportional to the change of tempreture."
 Mathematically
                             dE = mcdT = mc(T2 - T1)
                            
  where
                                m = Mass of the gas
                                c = A constant of proportional, known as speciefic heat.

Charles Law

This law was formulated by a Frenchman Jacque A.C. Charles in about 1787. It may stated in following two different forms:
 (1) "The volume of a given mass of a perfect gas varies directly as its absolute tempreture, whenthe absolute pressure remains constant.: Mathematically ,

                                          V / T = Constant
                                         V1/T1 = V2/T2 = V3/T3 = constant
(2) "All perfect gases change in volume by 1/273th of its original volume at 0degree C for every Idegree C in tempreture, when the pressure remains constant."

Boyle,s Law of Perfect Gases

This law was formulated by Robert Boyle in 1662. It states, "The absolute pressure of a given mass of a perfect gas varies inversely as its volume, when the empreature remins constant.:
Mathematically,
                                          pv = Constant

                           The more useful form of the above equation is :
                             P1V1 = P2V2 = P3V3 = ... = Constant
                  here suffixes 1, 2 and 3 ..... refer to different sets of conditions.

Properties of Perfect Gases

          A perfect gas may be defined as a state of a substance, whose evaporation from its liquid state is complete, and strictly obeys all the gas laws under all conditions of temperature and pressure. In actual practice, there is no real or actual gas which are ordinary difficult to liquefy, such as oxygen, nitrogen, hydrogen and air, within certain temperature and pressure limits, may be regarded as perfect gases.

Law Of Thermodynamics

There are three laws of thermodynamics.

1. Zeroth Law of Thermodynamics.

                                  This law states, "when two systems are each in the thermal equilibrium with a  third system, then the two systems are also in thermal equilibrium with one another."








2. First aw of Thermodynamics.

  This law states, "The heat and mechanical work are mutually convertible."

3. Second Law Of Thermodynamics.

                                  The second law of thermodynamics may be defined in many ways. but the two common statements according Kelvin-Plank and  Clausius are good.. in fig you can learn the second law yourself..

Thermal or Heat Capacity

The thermal or heat capacity of a substance may be defined as the heat required to raise the temperature of whole mass of a substance through one degree. Mathematically,
                      Thermal or heat capacity = mc KJ
     where
                        m = Mass of the substance in kg
                   c = Specific heat of the substance in kJ/kgK.

Thermodynamic Equilibrium

A system is said to be in thermodynamic equilibrium, if it satisfied the following three requirements of equilibrium.

1. Mechanical equilibrium. A system is said to be in mechanical equilibrium, when there is no unbalanced forces acting on any part of the system.
2. Thermal equilibrium. A system is said to be in thermal equilibrium, when there is no temperature difference between the parts of the system.
3. Chemical equilibrium. A system is said to be in chemical equilibrium, when there is no chemical reaction with the system.

Thermodynamic Cycle

When a process or processes ar performed on a system in such a way that the final state is identical with the intial state, it is then known as a thermodynamic cycle or cyclic process.