Don't know if it is an option BUT;
I worked on a electronic Wheel Chair Controller, also
drawing40-60 amps DC and had DC motors switched with Power Fets...
The mechanical relays used were off the shelf, BUT the software
controlled relays had a delay whereby the relays would NOT switch till
all current was at 0, then they would switch on/off.
This avoided contact arcing & pitting, which at those currents would not
take long....
Same thing, I used IR Power MosFets....great parts they were....
Hope that helps...\\
TDK
> -----Original Message-----
> From: Nagel, Michael [mailto:[log in to unmask]]
> Sent: Monday, July 30, 2001 8:03 AM
> To: [log in to unmask]
> Subject: Re: [DC] high-current relay
>
>
> Hello David!
>
> Ever thought of an IGBT?
>
> Best regards,
> Michael Nagel
>
>
> -----Original Message-----
> From: David Cary [mailto:[log in to unmask]]
> Sent: Donnerstag, 26. Juli 2001 23:18
> To: [log in to unmask]
> Subject: [DC] high-current relay
>
>
> Dear Designer Council,
>
> I'm working on a project where I need to switch a little over 60 A of
> current.
>
> I know I could just put lots of MOSFET transistors in
> parallel, and they
> will
> share the current. Just like light bulbs in parallel, if one
> is getting more
> than its share, it heats up, *increases* resistance, which
> redirects more
> corrent to the other items.
>
> It looks like mechanical relays are much cheaper, although
> they are only
> rated
> up to 40 A (something about UL rating ?).
> If I just put 2 relays in parallel to switch that 60 A, will
> they share the
> current properly (like MOSFETs) ?
>
> Is there any tech notes talking about putting relays in
> parallel ? I didn't
> find
> any at
> http://siemens.com/
> http://www.azettler.com/
> http://www.pandbrelays.com/
> .
>
> I hear that if I put lots of (BJT) npn transistors in
> parallel, when one
> gets
> more than its share, it heats up, *decreases* in resistance, then the
> positive
> feedback (``thermal run-away'') makes that transistor blow
> up, soon followed
> by
> its neighbors. That doesn't happen with relays, does it ?
>
> --
> David Cary
>
> --------------------------------------------------------------
> --------------
> -----
> DesignerCouncil Mail List provided as a free service by IPC
> using LISTSERV
> 1.8d
> To unsubscribe, send a message to [log in to unmask] with
> following text in
> the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
> To set a vacation stop for delivery of DesignerCouncil send: SET
> DesignerCouncil NOMAIL
> Search previous postings at: www.ipc.org > On-Line Resources
> & Databases >
> E-mail Archives
> Please visit IPC web site (http://www.ipc.org/html/forum.htm)
> for additional
> information, or contact Keach Sasamori at [log in to unmask] or
> 847-509-9700
> ext.5315
> --------------------------------------------------------------
> --------------
> -----
>
> --------------------------------------------------------------
> -------------------
> DesignerCouncil Mail List provided as a free service by IPC
> using LISTSERV 1.8d
> To unsubscribe, send a message to [log in to unmask] with
> following text in
> the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
> To set a vacation stop for delivery of DesignerCouncil send:
> SET DesignerCouncil NOMAIL
> Search previous postings at: www.ipc.org > On-Line Resources
> & Databases > E-mail Archives
> Please visit IPC web site (http://www.ipc.org/html/forum.htm)
> for additional
> information, or contact Keach Sasamori at [log in to unmask] or
> 847-509-9700 ext.5315
> --------------------------------------------------------------
> -------------------
>
---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
