1. Heat Transfer Model for a UI Core Inductor
Jamal Alsawalhi
School of Electrical and Computer Engineering Purdue University
11/16/2018

2. Outline Ways Heat can Transfer and Analogy to Ohms law
Goals to be achieved
Experiment Setup
Thermal Equivalent Circuit
Assumptions Made
Procedure for Experiment
Results
Uncertainties in Result
New Design Modeling
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3. Three Ways for Heat to Transfer
Conduction
∆T = q (L/kA)
k : Thermal Conductivity (W/mK)
Convection
∆T = q (1/hA)
h: Convection heat transfer coefficient (W/m2K)
Radiation
q = σ (T4)
T : Temperature of the black body
σ : Stefan-Boltzmann constant
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4. Analogy to Ohms Law Define R Therefore:-
Rconduction= (L/kA) (Note: Similar to Reluctance)
Rconvection = (1/hA)
Therefore:-
q  I
∆ T  V
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5. Goal of Experiment
Get an idea about the heat transfer in the UI core inductor at steady state conditions
In other words, need a mechanism that will allow predicting the surface temperature of the UI core inductor given a certain power input.
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6. Experiment Setup
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7. Experiment Setup
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8. Thermal Equivalent Circuit
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9. Two Major Assumptions
The heat distribution in the UI core inductor has reached equilibrium
Assume that the heat transfer due to radiation is negligible
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10. Applying Assumptions Rtot = 1/(2hA)  (Ts - Tamb) = q (1/2hA)
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11. Experiment Procedure Input a certain power and measure Ts
Determine h from the equation provided
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12. Results
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13. Uncertainties and Future Concerns
The dependency of h on the temperature change and geometry of problem
Is h the same for top and bottom surfaces?
Defining the area
Mechanism for measuring temperature
Covering the sides of the UI core with fiber
Time needed for equilibrium to take place
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14. New Design
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15. New design Thermal Modeling
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16. References
[l] W.G. Hurley, W.H Wolfle, J.G. Breslin, “Optimized Transformer Design: inclusive of high- frequency effects,” IEEE Trans. On Power Electron., VOL13, No.4, pp , July 1998
[2] W. H. McAdams, Heat Trasmission, 3rd ed. New York: McGraw-Hill, 1954, ch. 7
[3] F. Farahmand, F.P Dawson, J. D. Lavers, “Temperature Rise and Free Convection Heat Transfer Coefficient for 2-D Pot-Core Inductors and Transformers,” IEEE, 2005
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