Pages: [1]   Go Down
Author Topic: Quick 3 phase question  (Read 580 times)
0 Members and 1 Guest are viewing this topic.
0
Offline Offline
Newbie
*
Karma: 0
Posts: 30
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I have been looking into 3phase setups and one thing I wonder is, is it possible to have the 3 lower mosfets on the same heat sink hence tying them electrically together (sine the heatsink is conductive)? I know all the 3 top mosfets can be on the same heat sink. But I wonder if that also applies to the 3 lower.


Thanks!
Logged

Global Moderator
Boston area, metrowest
Online Online
Brattain Member
*****
Karma: 538
Posts: 27088
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Well, you have PNP/NPN type transistors drawn instead of P-channel/N-channel MOSFETs.

But anyway, the answer could be yes, as long as you select parts that have the 'tab' on the correct pin; and if not, yes if you use mica insulator/nylon spacer to insulate the tab from the heat sink.
See this as example, found thru a search at digikey.
http://www.keyelco.com/pdfs/M55p103.pdf
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0
Offline Offline
Newbie
*
Karma: 0
Posts: 30
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi,
All should be NPN
I want to use irfp250n http://www.hestore.hu/files/irfp250n.pdf
The metal heat sink back part is on the Drain. So I guess on the high side all 3 mosfets can be electrically connected and it won't be a problem. But I wonder if all 3 low side fets can be on one heatsink as well.
So having 1 heatsink for the high side fets and 1 heatsink for the low side fets.
« Last Edit: November 01, 2011, 09:28:36 am by nali2001 » Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 626
Posts: 34143
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

No you can't do that, the drain will be on the load not the supply.
You have to use insulated washers.
Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 30
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Thanks all,
I indeed see now.

At least the low side fets need to be all isolated.
Thanks!
Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 626
Posts: 34143
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

and the high side ones, if they are P-channel then it will be the source at the +ve supply.
If they are N-channel then they will only work as a source follower and do you want that configuration?
Logged

Pages: [1]   Go Up
Jump to: