a.c. relays

[spindown]

How is an a.c. relay constructed so it doesn't chatter? thanks Paul

[k7elp60]

At the top of the core just below where the armature contacts the core you will find a copper
ring. This ring holds the magnetic field when
the voltage goes to zero.

[dacflyer]

wow.. i always wondered that..
was wondering what the difference was between a ac/dc relay coils was...now i know <p>OW! OW! my head hurts now... i learned something new...OW!

[toejam]

mine too, that is stuff i never got taught, thanks k7elp60. Here's one for you; What would happen if you loaded a 12 guage shotgun shell with a rare earth magnet with very high flux density and popped the cap on it while it was incased in a 3 ft copper tube capable of handleing the pressure of the powder igniting?

[Chris Smith]

Alternate method is a bridge rectifier and a cap.

[dyarker]

copper ring - magnet field ????? and I was once told there were 60 turns clockwise and 60 turns counter-clockwise would you believe both polarities attract, and mass of armature keeps spring from opening while current changes direction?<p>linear induction by gunpowder - there must be a less noisy way to make a pulse.

[Chris Foley]

Google AC Relay Shading Ring for more information -- that's what the ring is usually called.<p>Good luck.
Chris

[spindown]

Thanks to all how responded. Very helpful Paul

[k7elp60]

Chris is right it is called a Shader Ring. When I did the first post I was going from memory. I went to my source, which is a Potter & Brumfield Technical Data book(SA65 printed 9-86) From page 13,"In order to operate a relay from A.C., relay manufacturers use a device known as a shader ring(or shader coil) on top of the core. Because of the shader ring, the magnetism developed in part of the core lags somewhat the magnetism of the remainder of the core. That is, there is a slight phase displacement between the magnetism of part of the core and the remainder of the core. Thus, as unshaded-core magnetic energy decreases to zero every half-cycle, the magnetic energy still present in the shaded portion of the core holds the armature sealed. By the time the energy in the shaded portion decreases to zero, coil and unshaded-core magnetic energy have begun to increase once again as current increase in value."<p>On a similar note I remember working on some control circuits that used AC relays and the relays were constructed to have a copper ring about as high as the armature winding. These relays had the charastic of being slow release. That is when the voltage to the coil was removed the relay stayed energized for a short time.
Merry Christmas
:p<p>[ December 24, 2003: Message edited by: k7elp60 ]</p>

[dyarker]

I'll buy that. Current in coil creates magnetic field in iron core, which creates current in copper ring. When current in coil decreases heading toward opposite polarity, magnetic field starts to colapse, decreasing current in the ring, the change of current in the ring creates magnetic field while coil current passes through zero. The ring is a one turn winding shorted to itself. Sorry k7elp60, the way I read your first post it seemed you were saying the magnetic field was stored in the ring.