Dear Designer's Council,

Thank you for your useful comments.

Chris Robertson <[log in to unmask]>
answered the literal question and said ``place relays
in parallel and they will divide the current equally.''.

"Kozlyk, Terry" <[log in to unmask]>
made some useful comments.

Steve Petry <[log in to unmask]> on 2001-07-26 05:53:18 PM
``a contactor ... essentially
large relays designed to carry large loads.''

"Nagel, Michael" <[log in to unmask]>
suggested IGBTs
and
Andy Serkuczewski / David Wager <[log in to unmask]>
pointed out the app notes on
  http://www.irf.com
.
>3. Choosing either a single MOSFET or an IGBT module you can then create
>your own custom-made solid-state relay using one of our photovoltaic
>isolators; see the attached data sheet on our PVI5033R series. ... See the
>attached AN-1017 application note for further information.

I found the app notes there and learned a lot of interesting stuff.
According to one of the app notes there, it's cheapest to use MOSFETs for
applications below 200 V,
IGBTs for applications above 1000 V, and analyze stuff in-between on a
case-by-case basis.

I work with electric motors that run off vehicle power. Typically 3 lead-acid
batteries, which my company calls ``36 V'' but automobile companies are calling
``42 V''. So I'm well in the MOSFET range.

Apparently people who design-in IGBTs live in a different world than I do. I
think of 200 V as a ``high'' voltage, but they consider 200 V the ``low''
voltage.

I'm still looking for ``contactors'',
and I'm glad I discovered the amazing
IRF1405 MOSFET: 55 Vdss, 131 Id; $3.38 in ones from Digikey.
(um... those are marketing numbers; it looks like it can switch a real 75 A,
which is more than I need, I hope).

--
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
---------------------------------------------------------------------------------