# Heat sink for tip36

#### nikhilsonar29

Joined Sep 26, 2014
68
hi,
good afternoon all
anyone can plz tell me what type of heat sink should I use to ic tip36 in the circuit
actually there are two rows of ic tip 36 in line. having 5 in each row.
Plz find the attachments for the circuit diagram.

#### Attachments

• 88.8 KB Views: 30

#### bertus

Joined Apr 5, 2008
20,228
Hello,

What will be the power dissipated in the transistors?
The power will determine the size of the heatsink.

Bertus

#### nikhilsonar29

Joined Sep 26, 2014
68
hello sir,
this circuit is for 3kva inverter circuit .
3kva is the power dissipation,
each transistor is capable of handling 25 amp current
Thanks And Regards
Nikhil

#### ronv

Joined Nov 12, 2008
3,770
Maybe a rough idea, but not exact.
3000kva @ 220 volts = 13.6 amps.
If it is 100% efficient (it's not) it would take 4.6 time as much from 48 volts = 62 amps.
The voltage drop across the transistor when it is on is 1.8 volts, so 112 watts in the transistors.
Each set is on half the time so 56 watts in each set or about 11 watts each.
If each set was mounted to the same heat sink and that one had a thermal resistance of 1 degree C per watt the heat sink would be at about 81C.
A 1 degree C per watt heat sink needs about 2500 square cm of surface area. So a big one with lots of fins.

#### MikeML

Joined Oct 2, 2009
5,444
Or a fan...

#### nikhilsonar29

Joined Sep 26, 2014
68
Thank you sir
i will consider this

#### ScottWang

Joined Aug 23, 2012
6,860
The rating current of Tip36 is 25A, normally we just count it only I=25A*(1/5)A=5A for the power dissipation reason.

You need to in series with a 0.2Ω/20W in the c for each Tip36, that is to protecting the Tip36.

Eff = Efficiency.
Wo = Output Power.
Wi = Input Power.
Vi = Input Voltage
Ai = Input Current
P80 = 80%
P90 = 90%

Wo = Wi * Eff% = Vi * Ai * Eff% = 220V*Ai*Eff% = 3KW
Wo = 3kW/52V = 57.7A

If Converting Efficiency = 80%
Wi_P80 = Wo/Eff% = 3kW/80% = 3750W
Ai_P80 = Wi/Vi = 3750W/220V = 17A

If Converting Efficiency = 90%
Wi_P90 = Wo/Eff% = 3kW/90% = 3333W
Ai_P90 = Wi/Vi = 3333W/220V = 15.15A