Is there a more robust alternative to IRF3205 MOSFET? / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Is there a more robust alternative to IRF3205 MOSFET?

1 2 3 4 next last

Move Thread

LAN_403

Steve Hobley

Sat Nov 20 2010, 06:19AM

Registered Member #1731 Joined: Thu Oct 02 2008, 02:22PM
Location: Indiana
Posts: 52

I recently built the 24v version of the Skori Tesla coil.

Schematic:

The performance is outstanding but I've blown 2 IRF3205 MOSFETs already.

Since there is a 5 amp fuse in line with the coil/mosfet and the 3205's are rated at 110A I'm assuming it's not the current that is blowing them, but the voltage (55v is not much more than double the 24v input).

Is the primary coil picking up feedback from the secondary and this is kicking back across the source/drain?

Is there a "tougher" Mosfet I can try in place of the 3205's?

Steve

Tesla Fan

Sat Nov 20 2010, 07:28AM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

Hi,

First of all excellent coil, it looks really good on youtube!

As for an 110A MOSFET i canâ€™t think of something and i think that TO-220 and TO-247 packages do not get much more than 250W (280W is the biggest i know of), and you are at 200W with the IRF3205, so for more voltage you will have to sacrifice some amps i think... Also i think the 3205 MOSFET is selected very well, as it has the smallest Rds and the bigger amps ratings (of the ones i know at least).

Here is a comparison for some of the MOSFETs i know:

NAME______VOLT___AMP___Rds_____WATT
IRF3205_____ 55____110___0.008____200

IRFZ44______60_____50___0.028_____150
IRF740_____400_____10____0.55_____125
IRFPF50____900_____6.7____1.6______190

IRFP150____100_____41____0.055_____230
IRFP240____200_____20____0.18______150
IRFP250____200_____30____0.085_____190
IRFP260____200_____46____0.055_____280
IRFP350____400_____16_____0.3______190
IRFP460____500_____18____0.27______220

So maybe an IRFP150? But it can handle less than half the amps... Do you know how many amps you use? 5 amps fuse sounds small, why use a 110A MOSFET in the first place? Do the IRF3205s get any hot?

-EDIT-

Found a couple:

IPP05CN10N G , Digi-key

Datasheet

MTY100N10E , Digi-key

, Datasheet

Both good for 100V 100A (300W) !

Steve Conner

Sat Nov 20 2010, 10:54AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

You can blow a MOSFET with much less than its rated current if it's not turned fully on. Check the gate drive etc.

Also, the rated current is with an infinitely large heatsink, unattainable in practice. I usually shoot for about half of it.

Steve Hobley

Sat Nov 20 2010, 01:44PM

Registered Member #1731 Joined: Thu Oct 02 2008, 02:22PM
Location: Indiana
Posts: 52

Thanks for the replies.

Is there any way to protect the MOSFETS? I bought a lot of them, but I'm starting to work through them. :)

I don't have any problems with the 12v version of the coil - so I am assuming that the increase in voltage is to blame.

If it turns out it is the current, then maybe I can add more fuses to the primary coil connector?

Steve

Tesla Fan

Sat Nov 20 2010, 01:51PM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

If you know how much amp MAX your MOSFETS can handle, why not placing a fuse to the pin of the MOSFET (Drain)? I am not sure you could do that but is sounds like a good idea to me.

Adam Munich

Sat Nov 20 2010, 04:05PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Why not just go for the IRFP260's? They are relatively cheap, they have a max voltage of 200, and a max amperage of 46. With my ZVS I can push 1.3kW out of a FBT @36v, and since my driver seems to be 80% efficient I am pushing somewhere around 44 amps through them! Aside from heat there are no problems at all. With a fan on the tiny heatsinks I can get about 60 seconds run time before they get too hot, so with a big heatsink it'd probably last forever. You can get huge heatsinks out of old stereo receivers.

quicksilver

Sat Nov 20 2010, 04:14PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Great job!!! Neat & clean. It really looks like something to be proud of !
It MAY simply be an issue of inefficient heat dissipation. There may be a degree of wattage adjustment (resistors) or other simple adjustment that was not taken into account (spacing of components). Just guessing of course but perhaps the original design did not take into account longer operational runs greater than a minute.

The idea of a fuse at the drain appears to be a good idea. However it may not tell you why this is occurring. In my limited experience the design of all heat dissipation agenda may be more important than it appears for longer runs. I've personally seen a situation where a more robust design that allowed for effective heat dissipation was an effective answer. However, from the schematic, it appears that the resistors may be1 watt. Is it possible that is an issue? The choices for FETs appears that you're pretty much at the top of the heap.

AleSeg

Sun Nov 21 2010, 03:18AM

Registered Member #2727 Joined: Tue Mar 09 2010, 02:39PM
Location: Montevideo - Uruguay
Posts: 33

Hello.
I saw the movie on youtube and I have a doubt about the upper spherical electrode. Is very close to the last turns of the coil, and therefore should behave as shorted turns.
Have you tested the possibility of increase the distance between the upper electrode (the top load) for overcame this problem?
Perhaps in this way you will achieve better performance.

Greetings

Steve Hobley

Sun Nov 21 2010, 04:28AM

Registered Member #1731 Joined: Thu Oct 02 2008, 02:22PM
Location: Indiana
Posts: 52

Again - thanks for all the feedback - much appreciated.

I will look into the IRFP260's and also look into the heatsink issue - I have a largish piece of L shaped aluminum attached directly to the case with thermal compound on the joints - the MOSFETS don't seem to be getting that warm, but I only test them by touch afterwards.

You are correct about the coil top - the very top of the coil is finished with aluminium tape to give a circle of contact with the top load. This is something I've been doing lately on some of my other coils, without too much trouble.

I will certainly look into adding some form of spacer.

Steve

Tesla Fan

Sun Nov 21 2010, 01:15PM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

Is that a 24V SMPS at the base of the coil? I have a few questions i want to ask you if you can spare the time, i have sent you a pm

1 2 3 4 next last

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob