Re: Contactor question, Arc Suppression

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

There is a "trick".  I am not sure it is worth all the trouble...

You make a circuit the monitors the current and voltage along with 
some delay electronics.  The idea is to only open the contactor when 
the current passes through zero.  Close it as the voltage passes 
through zero...

Then, the contacts only have to take the nominal current rather than 
peak or break situations...  But the circuit and all the trouble it 
takes to make it has to be balanced against just getting a really big 
contactor in the first place...

It can be done with some simple stuff in very controlled situations, 
but it is sort of an "art form"...

An alternate is to get contactors with fail safe switches that detect 
a failed contact.  If it welds closed, a warning goes out...

Contactors weld closed all the time...  Probably their #1 failure mode....

Maybe best to use really big hydraulic circuit breakers...  They know 
how to hand the big currents ;-))

Cheers,

	Terry