[Amps] AC to DC

[John Popelish]

Bill Turner wrote:

> I wish I could remember exactly, but years ago I heard some advice 
> against using DC on AC relays. It had to do with the core getting 
> magnetized or something like that, which delayed dropout when power 
> was removed.

Yes, DC relays often have a thin film of nonmagnetic material between 
the coil core and the armature (the iron part it attracts), to keep 
the remnance from getting strong enough to hold the relay closed after 
the coil is de energized.  AC relays almost always have a solid copper 
shunt ring around half of the tip of the coil core, to retard the 
phase of the field through the surrounded fraction of the core, to 
produce two separate pulsing sections that take turns holding the 
armature down, so it doesn't buzz as the AC current goes through zero.

If you want to experiment with your relay, I suggest you find (by 
experiment) what DC just pulls it in, and then put double that voltage 
across the coil for a while, and check for any signs of overheating. 
If there is none, That is about what I would use to activate the 
relay.  If it sticks on, you will have to epoxy a dot of paper on the 
tip of the core or the armature where it touches the core.  A few mils 
is usually enough.