On Fri, 17 Aug 2007 08:01:28 -0700, Steve wrote:

How does an AC relay work? I understand that the magnetic field of a
DC relay coil attracts the contact arm and I assumed an AC relay just
had a diode to convert coil current to DC - however when I tried to
find an AC relay fault there was no diode. I thought 50 or 60 Hz
alternating magnetic field cannot produce such a corresponding
movement in a mechanical contact arm so I would have thought the net
magnetic effect would be zero (no overall attraction or repulsion).
Given the relay obviously operated before, I just can't see how. I
did think the 'AC' rating just meant the contacts but I don't see why
this wouldn't just be a current rating.

Enough latent magnetism in the core to somewhat negate the alternating
field? Same goes for an AC solenoid as in a doorbell plunger I suppose.