"NSM" wrote in message
news:aPvvd.23287$U47.20358@clgrps12...

"James Sweet" wrote in message
news:iJvvd.4172$N%6.261@trnddc05...

| It isn't easy to mechanically interlock relays.

| Why would you need to though? Just use multipole, double throw relays
and
| you can wire them together to do just about anything you want. I missed
the
| exact function of the original device though.

Hard experience has taught us that when a motor is operated both forward
and
in reverse, it is best to make damn sure both contactors cannot close at
the
same time no matter what. Thus the choice of a mechanical interlock system
so that even if the contacts weld closed on one side the other contactor
cannot close.

NM (Electrician)



With a DC motor if both close at once it should behave exactly as it does
with both open, both sides of the motor are connected to the same supply
rail and nothing happens. If it's a reversible AC motor I'd have to look at
the wiring to find out what happens, but I would think the worst case would
be a blown fuse, we're not talking a 10hp 3 phase industrial motor here.