Re: FS: Transco Y Relay

Alan G0XBV

Andy, Peter - that is fascinating stuff.  I just couldn't fathom how it wouldn't hum and chatter!
Many thanks!
Alan G0XBV 

-----Original Message-----
From: Peter Torry peter.torry@... [ukmicrowaves]
To: ukmicrowaves
Sent: Fri, 18 Mar 2016 14:12
Subject: Re: [ukmicrowaves] FS: Transco Y Relay

Digging back into my memory I recall that AC relays used a laminated iron core to reduce Eddy current losses and hysteresis losses.  To avoid chatter and humming of the armature part of the pole face had a shading ring fitted. The flux created in this ring, usually copper, is phase shifted relative to the flux in the main core so preventing the main flux from periodically going through zero.
Its a long while since I had a connection with relays rather than just using them.




On 18/03/2016 12:37, Andy Talbot andy.g4jnt@... [ukmicrowaves] wrote:
I believe the purpose of the "shading ring" on AC solenoids is to continue the flux - ie effectively keep a current flowing - during the low portion of the sine.  Quite how it does it I don't know, but I'm just delving into memory of many many decades ago.  

 It would have to use non linearities in the core material to work though, as harmonics of the AC flux  would have to be present to fill in the gaps

Got me pondering now - having just also remembered shaded pole motors.   I didn't understand them then (1970's) and still don't know exactly what the shorted turn does.



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