Maker Pro
Maker Pro

2N3055's and heat

BobK

Jan 5, 2010
7,682
Joined
Jan 5, 2010
Messages
7,682
A center tapped transformer cannot be wired for double the current at half the voltage. A transformer with 2 windings (4 wires) can. If your transformer is like that, you could have a switch to have 2 ranges of voltage and you would save power on any voltage < 18V when using the lower range.

If it is really centered tapped, you can still do the same, but you will not double the current output.

Bob
 

John Potter

Nov 20, 2016
4
Joined
Nov 20, 2016
Messages
4
A reply to all - I hope that's OK
The other reason I chose a linear device was because a friend said it was better. The reason - he's a radio ham and is paranoid about interference. When I told him i was making a Joule thief he went purple. I then said i would make a 100W one and add a 100 foot aerial. Not a titter.

In regard to the quality of 2N3055's mine are all steel. However there are a lot of fakes around. Good little video on Youtube - chap cuts the case off a good one and a fake. The fake one is almost empty, these are failing at 30V and 1A. I have 4 x 2N3055's from the US and 4 from CPC UK.

If the idea I have proposed above works then this linear regulator gets nearer reality and more than a learning challenge. Come to think of it it might even work.
I shall be dropping from 26V to 2V =24V or 52V to 26V = 26V ?
That's better than 52V to 2V = 50V.
3.33A x 26V = 86W spread over 4 x 2N3055's. The fan cooling and the heat sinks I have looked at are just under 1C/W - roughly 22C + ambient.
If that = 50C then the 2N3055 junction is going to be 76C. ( I have read it's 1.52 x case C Max).

Thanks shrtrnd. It looks like I may well have to use your advice if what I have goes fut.

I do thank you all. It's not always easy to follow all of some comments but I'm running at better than 90% which for an old f**t isn't too bad.

Tonight I am having an early night, it's 22.47 hrs and the dog needs her beauty sleep.
Thanks again all.
 
Top