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Old 11th August 2010, 08:07 PM   #2891
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Quote:
Originally Posted by AndrewT View Post
R1=22r is not 500mA.
What is R1?
the CCS dissipation is [Vin - Vr1 - Vout] * Iccs
I'll guess at some inputs:
Vin =61V
Vr1 =2V
Vout = 46V
Iccs =0.5A
Pq1 = 6.5W
Ta=25degC

It would take quite a few seconds even with a tiny heatsink to burn out the CCS FET. With an small but adequate sink say 10C/W the sink rise would be 65Cdegrees above ambient.
Tc ~ 70Cdegrees above ambient. That puts Tc ~95degC
The temperature de-rating for the FET is 0.44. [150 - 95] / [150-25]
Your 150W FET is de-rated to 66W
Pq1 ~ 10% of maximum rating.

If the FET is cold it is not passing current.
It has almost certainly not been damaged by over-voltage.
It may have been damaged by soldering or handling or simply the circuit has a fault.
R1 is 3R8 to get 500mA
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Old 11th August 2010, 08:08 PM   #2892
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150R 10W before the reg measure 54V
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Old 11th August 2010, 09:22 PM   #2893
AndrewT is offline AndrewT  Scotland
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the current is ~0.5A
The dropping resistance is 150r
How hot does it get?

Have you done the arithmetic?
P=I*I*R=37.5W

Why use 10W resistor?

Why use 150r?
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Old 11th August 2010, 09:38 PM   #2894
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AndrewT you are right was a bad connection 2nd mosfet, now is all ok after adding the 150R 10W in series to lower till 54VDC after reg, this reg after 15 minutes the heatsink don't hot & the other heatsink it's hot....
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Old 11th August 2010, 09:44 PM   #2895
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Quote:
Originally Posted by AndrewT View Post
the current is ~0.5A
The dropping resistance is 150r
How hot does it get?

Have you done the arithmetic?
P=I*I*R=37.5W

Why use 10W resistor?

Why use 150r?
It's very very hot can left the finger few seconds.

Salas told me start with 10R 10W...

To low the voltage to 55VDC after the reg.
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Old 11th August 2010, 11:56 PM   #2896
Salas is offline Salas  Greece
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Is it CRC or RC configuration? From bridge to filter cap (+) just a resistor is RC. Is there a capacitor before the R?
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Old 12th August 2010, 10:08 AM   #2897
RCruz is offline RCruz  Switzerland
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Hi Salas

For the zobel on the output, can I use 0,5w 1r resistors ?

What is the minimum power requirements ?
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Old 12th August 2010, 10:56 AM   #2898
Salas is offline Salas  Greece
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No power requirements. 1/4W OK.
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Old 12th August 2010, 11:48 AM   #2899
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Quote:
Originally Posted by Salas View Post
Is it CRC or RC configuration? From bridge to filter cap (+) just a resistor is RC. Is there a capacitor before the R?
It's CR so after PSU filter cap (+) the resistor & after connected the reg.
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Old 12th August 2010, 11:53 AM   #2900
Salas is offline Salas  Greece
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Do it the other way. Bridge to R to cap. 10R and see. Maybe you will need even less.
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