OT: Clamping Diodes/AC relays
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> >As for AC relays using special laminates...I am not familiar with them
but I
> >don't understand how they would keep the magnetic field constant enough
to
> >hold the armature closed during the entire + to - cycling of the AC
waveform!
> >Please enlighten me! (learn something new every day!)
*****************************
If you look closely at an AC relay, you should see a copper ring set into a
slot in the pole piece. It behaves like a shorted one-turn winding. The AC
field of the relay coil induces a current into this ring that is almost 90
degrees phase lagging the current in the relay winding. So when the magnetic
field of the main winding passes through zero, the lagging current in the
copper ring has not yet zeroed. The result is that there is never a time
where the total flux at the pole face is zero. The reason for the ~90 degree
phase lag is that the copper ring is like a winding with more inductance
than resistance. The relay coil current is more "in phase" with applied coil
voltage because it has a much larger resistance to inductance ratio.
Ray McArthur
but I
> >don't understand how they would keep the magnetic field constant enough
to
> >hold the armature closed during the entire + to - cycling of the AC
waveform!
> >Please enlighten me! (learn something new every day!)
*****************************
If you look closely at an AC relay, you should see a copper ring set into a
slot in the pole piece. It behaves like a shorted one-turn winding. The AC
field of the relay coil induces a current into this ring that is almost 90
degrees phase lagging the current in the relay winding. So when the magnetic
field of the main winding passes through zero, the lagging current in the
copper ring has not yet zeroed. The result is that there is never a time
where the total flux at the pole face is zero. The reason for the ~90 degree
phase lag is that the copper ring is like a winding with more inductance
than resistance. The relay coil current is more "in phase" with applied coil
voltage because it has a much larger resistance to inductance ratio.
Ray McArthur
Comments
behind this! Thanks for the lesson and the info!
[noparse][[/noparse]Non-text portions of this message have been removed]
> > >As for AC relays using special laminates...I am not familiar with them
>but I
> > >don't understand how they would keep the magnetic field constant enough
>to
> > >hold the armature closed during the entire + to - cycling of the AC
>waveform!
> > >Please enlighten me! (learn something new every day!)
>
>*****************************
>If you look closely at an AC relay, you should see a copper ring set into a
>slot in the pole piece. It behaves like a shorted one-turn winding. The AC
>field of the relay coil induces a current into this ring that is almost 90
>degrees phase lagging the current in the relay winding. So when the magnetic
>field of the main winding passes through zero, the lagging current in the
>copper ring has not yet zeroed. The result is that there is never a time
>where the total flux at the pole face is zero. The reason for the ~90 degree
>phase lag is that the copper ring is like a winding with more inductance
>than resistance. The relay coil current is more "in phase" with applied coil
>voltage because it has a much larger resistance to inductance ratio.
I've never seen such a ring when the core (or moving pole piece) is
laminated. It strikes me I might have seen something like this if the core
was a solid slug, but don't take that to the bank.
Jim H
Original Message
> >If you look closely at an AC relay, you should see a copper ring set into
a
> >slot in the pole piece. It behaves like a shorted one-turn winding. The
AC
> >field of the relay coil induces a current into this ring that is almost
90
> >degrees phase lagging the current in the relay winding. So when the
magnetic
> >field of the main winding passes through zero, the lagging current in the
> >copper ring has not yet zeroed. The result is that there is never a time
> >where the total flux at the pole face is zero. The reason for the ~90
degree
> >phase lag is that the copper ring is like a winding with more inductance
> >than resistance. The relay coil current is more "in phase" with applied
coil
> >voltage because it has a much larger resistance to inductance ratio.
>
> I've never seen such a ring when the core (or moving pole piece) is
> laminated. It strikes me I might have seen something like this if the
core
> was a solid slug, but don't take that to the bank.