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### Topic: Power dissipation IGBT sanity check (Read 180 times)previous topic - next topic

#### morrisonandboyd

##### Jun 12, 2018, 09:58 pm
Hi was hoping for a sanity check.

Looking at a FGY75N60SMD IGBT

Driving at 50 Khz, 50% duty, 75A, 311V DC

Was trying to figure heat dissipation in device.

I calculated 236 watts switching loss, and 54 watts of resistance dissipation (call it 300 watts)

Device is rated to 375 watts.

Switching loss is 4.71mJ (x 50,000 cycles/ second) = 236j/sec= 236watts

Resistance loss calculated from Saturation voltage characteristics (fig3 in Fairchild data sheet Rev C2)

R=(deltaV)/(Delta Amps) = 1.4V/146Amps) = 0.0096 ohms

P = I*I*R = 75A*75A*(0.0096) = 54

Have I missed anything besides the obvious need to quench this thing in the Mississippi river??

Thanks,

MB

#### TomGeorge

#1
##### Jun 13, 2018, 12:24 pmLast Edit: Jun 13, 2018, 12:36 pm by TomGeorge
Hi,

Load = V * I = 311 * 75 = 23325 Watts (23.3kW)
At 50% duty = 23325/2 = 11662.5 Watts

Your IGBT losses = 236 + 54 = 290 Watts

Switching efficiency= 11662.5 / (290 + 11662.5) =0.975 == 97.5%

Sounds pretty good.
You will need a decent heatsink and forced cooling, some more equations to play with.

Tom...
Everything runs on smoke, let the smoke out, it stops running....

#### morrisonandboyd

#2
##### Jun 13, 2018, 01:45 pm
Thanks Tom!,

Appreciate second set of eyeballs.

MB

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