Re: FS: Transco Y Relay

John E. Beech

The reason AC relays work is because both polepieces are magnetized by the energizing current. The shorted turn acts like a transformer and increases the magnetizing current at the pole piece. This induced current is in antiphase too the main magnetizing current ( Lenz's Law). This ensures that the magnetic pole is of opposite polarity thus the stator and amature always attract each other irresspective of the direction of current flow. The shaded ploe motors usually have two shorted turns on each pole, one offset from the other so that the  motor always starts rotating in the forward direction.

de John G8SEQ

  -------Original Message-------
From: Andy Talbot andy.g4jnt@... [ukmicrowaves]
To: ukmicrowaves@...
Subject: Re: [ukmicrowaves] FS: Transco Y Relay
Sent: Mar 18 '16 12:54

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.

On 18 March 2016 at 12:31, ALANNOTTAGE@... [ukmicrowaves] <ukmicrowaves@...> wrote:


-----Original Message-----
From: ALANNOTTAGE@... [ukmicrowaves] <ukmicrowaves@...>
To: ukmicrowaves <ukmicrowaves@...>
Sent: Thu, 17 Mar 2016 16:47
Subject: Re: [ukmicrowaves] FS: Transco Y Relay
>Chris made reference to the coil resistance of the relay.  I have an Amphenol relay with a 110VAC coil.  I believe it's R is ~550 ohms.  It's not to hand just now, but I will check it later.  Thanks to Peter for that rule of thumb - I will need to know that >too at some stage!
The spec of my coil is 550 ohms and measures out nearer to 500.  In comparison, the 26V DC models are all around 200 ohms.  From a DC perspective, that would seem to bear out everyone's experiences then.  I still have no idea how they actually work with AC applied :>)



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