Since the current is heading in both directions, (AC), this adds another level of complexity to a solid state switch although SCRs etc. would be quite feasible. But I'd use a contactor & keep it simple. They also tend to handle short circuit faults etc. a bit more graciously. RP Hi Denny Yes you are correct, see its not really my field :-). This is only very low frequency, basically it is to switch an altenator output to one of a bank of batteries for charging which will have a large hysteresis factor built into the time. Thanks Jon --On Thursday, August 14, 2003 7:29 PM -0400 Denny Esterline wrote: > Hi Ron, > I have too say this would be dependant on the rest of the device. > At very low switching frequencies (every few minutes or less) I might > consider a relay. However mechanical contacts are subject to bounce, both > mechanical and electrical, creating interference and noise for other > systems, that may be undesirable. > > If your controlling motors or lighting, or -lots of other stuff- you might > want to move to a PWM variable control, which would mandate solid state > power handling. There are a wide variety of devices that could handle this > MOSFETs, BJTs, and IGBJTs immediately come to mind. > > Ultimately the decision has to be based on the application. Perhaps we > could be more helpful if you shared a few more details about what you're > trying to do? > > Denny > > > ----- Original Message ----- > From: "Jon Jenkins" > To: > Sent: Thursday, August 14, 2003 7:17 PM > Subject: [EE] Switching large currents > > >> Hi People >> >> I am not sure if this is the correct forum or not. >> >> I am building a small system with PIC control which >> has to switch large currents +30A at 12/24V. This >> is not really my area so I need some advice. >> >> Without wanting to start WWIII what do others >> see as the pros and cons of the various methods >> electronic and mechanical. >> >> Thanks for any input. >> >> Jon -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu