# Measure temperature and power losses?

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##### Member
I think it is better if you check my model, cause I am not sure what to change when it comes to coils and capacitors.
I skipped the capacitors and inductors since they can't be losses measured. I need to hand calculate those.

I want to find the temperature of all the components that are included in table that I have attached. You can also see the average power losses from LTspice.

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#### ronsimpson

##### Well-Known Member
R3, R6 1M resistor:
Most small resistors will not survive 600 volts. You need to find a high voltage resistor. (or use resistors in series)
Next find the average voltage and current. watts. Choose a resistor that can withstand that power.
A 1W resistor with 1W of power will almost melt the solder.
I usually run resistors at 1/2 power to keep the temperature down.
(you must choose a real part before you can get the temperature)

D1,3,4,5:
Spend some time with the data sheet. It looks like the maximum temperature is hit at 1.1V @ 1A. So it is a 1.1 watt diode. Max temp 150C junction temperature.
Question to you; Is this the right part? Is your average current above 1A or below 1A?

##### Member
But this those values for the resistors was standard value from the demo. Since this is a simulation, do I really need to find real parts?
I am not sure if I can find a high voltage resistor in LTspice or how large should the series resistors be.

Hmm, did you check the temperature? I may have selected the wrong parts, but I do not have how to select the correct ones i LTspice. The average current is higher than 1 A.

#### ronsimpson

##### Well-Known Member
do I really need to find real parts?
No. SPICE does not make smoke or fire. You can put 600 volts on a 35 volt capacitor and nothing bad happens.

I think the exercise of picking a real resistor is much like picking the right diode.

In the case of your transistor, we need to know how much power, then pick a heat sink.
I used a R6020ANX which is 600V, 50watt transistor in a to-220 case. But 50 watts is with a infinite heat sink.
With no heat sink the temperature goes up by 70C/watt. (25C room temp, 1 watt=delta of 70C = 95C )
Probably you will need to pick a heat sink with a known thermal resistance.

##### Member
Hmm, I am not able to find "R6020ANX " in my library. Is it not included maybe, is that transistor an external part? Yes, a heatsink is probably needed.

--edit--
the choice of the components in LTspice would effect the efficiency and losses right?

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#### ronsimpson

##### Well-Known Member
I am not able to find "R6020ANX " in my library
And I can not find the R6020PNJ in real life.
The ANX/PNJ is the case style. The R6020 is the silicon.
Table of case styles that I can find:
ENZIC9 = TO-247
ENZIC8 = TO-3P
ANX = TO-220
KNJTLTR = TO-263
To know the temperature of a part you need to know how much power AND the thermal resistance. (how that power gets to the air)
Each case has a different resistance to air and a different resistance to a heat sink.

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