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21st August 2017, 08:31 #1
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Common heatsink Calculation
I want to use the common heatsink for the Bridge rectifier,IGBT and Boost Diode.
I have calculated the Each of the Dissipation
P_DIS_Bridge=18w
P_Dis_igbt=24w
P_boost_diode=6w
RJC_BRIDGE=0.6DEGREE/W
RJA_BRIDGE=1.63 DEGREE/W
RJC_IGBT=0.58 DEGREE/W
RJA_IGBT=1.66 DEGREE/W
RJC_Diode=0.85 DEGREE/W
RJA_Diode=6.66 DEGREE/W
TJ=90 DEGREE
TA=50 DEGREE
How to calculate the common heatsink for all 3 power components...??

21st August 2017, 09:14 #2
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Re: Common heatsink Calculation
Hi,
Any heatsink calculaton document will give this information. Read through them.
RJA is not valid for your situation, because you use a heatsink.
(RJA is for use without heatsink)
RJC is for use with heatsink.
RJC x power_dissipation gives the difference temperature between junction and case.
Calculate this for each device.
Take the max value of those three.
Take TJ  max_vlaue to get max_heatsink_temp at full load. (add some margin for difference temperature between device_temp and heatsink_temp)
Then calculate the difference between TA and max_heatsink_temp = allowed heatsink_temperature_rise.
Heatsink value = allowed heatsink_temperature_rise / total power dissipation.
Klaus

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22nd August 2017, 07:44 #3
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Re: Common heatsink Calculation
Hello KlauuST
I have calculated a per your suggestions.
Normally all datasheet have provided data of R(JC) IN degree/w but the attached ipm provided it in kelvin/w.
Now it hard to handle.
Can you pls advice how to convert the same in degree/W
I google 3k/w in kelvin to degree Calculator and it is coming 270degree/w and whole result is getting wrong.
Pls advice on the same
   Updated   
Here is the attached image

22nd August 2017, 08:07 #4
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Re: Common heatsink Calculation
Hi,
For temperature rise, which is a relative change in temperature K and °C is the same.
Lets say the temperature rises from 25°C to 60°C.
The temperature rise in °C is: (60°C  25°C) = 35°C
25°C = (25 + 273)K = 298K
60°C = (60 + 273)K = 333K
The temperature rise in K is: (333K  298K) = 35K
For all relative temperature calculations you may use the same value in K as in °C.
5K/W for relative calculations is the same as 5°C/W.
Klaus

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22nd August 2017, 08:31 #5
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Re: Common heatsink Calculation
No need to convert between degree C and K for a linear heat dissipation problem.
It's the simple point that thermal resistance has the commonly agreed unit K/W, although degree C/W is the same number because you are measuring temperature differences.

22nd August 2017, 08:57 #6
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Re: Common heatsink Calculation
Hello Guys..
Understand..
Now what problem i am facing here is.
Power dissipation per igbt =15.68 (There are 6 igbt inside the ipm module)
TJ=90 Degree
TA=60 Degree
JunctiontoAmbient Thermal Resistance=(TJTA)/Power dissipation across single igbt)=(9060)/15.68=1.97degree/Watt
Now,
R(heatsink to ambient)=ØJA(ØJC+ØCH)=1.97(3K/W+0.2)=0.8
This is the problem i am facing..?
   Updated   
For The final calculation
RSA_IPM=(TJ1TA)P_IPM(RJC4+RCS4)/(Total heat dissipated)
TJ1=90
TA=60
P_IPM=Heat dissipated in ipm=15w
RJC4=3K/W
RCS4=0.2D/W (For silpad)
RSA_IPM=((9060)15(3+0.2))/140=363degree/w

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22nd August 2017, 10:06 #7
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Re: Common heatsink Calculation
Hi,
This is the problem i am facing..?
RJC4=3K/W
* maybe there is additional information or there is an errata...
And there is a mistake in your calcualtion.
The result of your formula should be 0,129K/W
And were do the 140W come from?
Klaus
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22nd August 2017, 10:19 #8
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Re: Common heatsink Calculation
https://www.mitsubishielectricmesh....S92F6AG_N.pdf
The Addition of all heat dissipated.
1) Bridge Rectifier:18w
2) IGBT_PFC=24W
3)Boost=6W
4) IPM=15*6=90W
TJ1TAP_IPM*6*(RJC4+RCS4)/(Total heat dissipated)
YES IT IS 0.129K/W

22nd August 2017, 10:50 #9
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Re: Common heatsink Calculation
Hi,
according datasheet the 3K/W is true.
So with a disspated power of 15W per IGBT you already get a temperature difference of 15W * 3K/W = 45K between junction and IBGT case.
This means if you want to limit junction temperature to 90°C (why that low? datasheet says 150°C) then the IGBT_case temparature needs to be less than 45°C.
This is impossible with 60C ambient temperature.
Klaus
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7th September 2017, 05:05 #10
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Re: Common heatsink Calculation
Yes.. now by the calculation
Thermal resistance of the Heatsink is 0.133°C/W
How heatsink area calculation works..??
How to design customised heatsink for Aluminium type.
Regards
Marx
   Updated   
Yes.. now by the calculation
Thermal resistance of the Heatsink is 0.133°C/W
How heatsink area calculation works..??
How to design customised heatsink for Aluminium type.
Regards
Marx
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