Contactors with Mechanical Device to Clamp Moving Magnet to Fixed Magnet

http://uk.rs-online.com/web/c/?searchTerm=Bistable+relay&sra=oss&r=t

They are called mechanical latching relays, and they already exist.

Latching relay or latching contactor as Tornado has said have already been done.

Most latching contactors use a permanent magnet to hold it closed and spring force to hold it open. Using the electromagnetic coil to force it closed or open.

Which by the way is not inherently fail-safe, so keep that in mind when using them...

i was part of the team which designed a Lighting Control contactor for GE USA...you can get details from the US Patent #6628184. This is a mechanically latched contactor with a pulse-On / pulse-Off design. Interesting concept. We are proud of it

There are also electronic pulse relays commonly available that can do the same thing.

Is this for a specialised application where no industrial product alternative exists or are you trying to reinvent the wheel?

What exactly is the application and load?

As other members have said, there already are latching relays; but you need two separated signals: Set and Reset.

You might want to try a digital toggle switch, so you turn it ON with one pulse and OFF with the next.

Connect Q to this transistor driver thru the 1k resistor and you're done.

Not a good drawing, I know, but see if that's what you need.

Regards

just curious? whats your motivation? trying to save energy consumption in control circuits?

Also called bistable relays.

Attach a jumper from the "output" side of the relay to the coil.

Oh wait...you want it to remain closed even if you decide not to send power through that relay. Power is intermittent. How did you want to unlatch the relay again? A second pulse? Sounds like a latching relay.
A second coil?

Check the manufacturers catalogs for Mechanical Latch.

Most of them have them already for their contactor ranges (not for all the sizes though!). Telemechanique / Schneider for sure.

These are additional units that are attached to the normal contactor (Top) and will hook on the moving part. When the main coil is energised, it pulls the latching mechanism in. This will keep the moving part blocked in. To release, you send another pulse to the coil of the mechanical latch unit. This will release the hook and release the contactor's moving part.