Re: AC feed fail changeover relay

2003-02-26 Thread John Woodgate

I read in !emc-pstc that bruce maule bruce.ma...@alliedtelesyn.co.nz
wrote (in se5cab2b@leo.alliedtelesyn.co.nz) about 'AC feed fail
changeover relay' on Wed, 26 Feb 2003:

I believe that this scenario is reasonably common, from talking over with our 
electrical safety test lab, but the solution of using a single relay as the 
changeover element may not be viable.

You can use a relay with two normally-open and two normally-closed
contact sets. Provided the insulation between the contact sets meets
basic-plus-supplementary or reinforced requirements, you can wire the
supplies through two contact sets in series. The contact gaps when open
may need to be 3 mm or some other minimum length, depending on your
national regulations. 
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
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AC feed fail changeover relay

2003-02-25 Thread bruce maule

Hello all,

Would anyone know of a relay suitable for the following application:

The circuit is a 100-240VAC ac feed fail changeover, ie one output with an A
and B ac feed.

The coil would be powered from 48VDC derived from either ac feed and the
contact rating would need to be in the range 15 to 30A.

The main design challenge tripping up the designer - and hence my involvement
- is in maintaining double/reinforced isolation between the A and B inputs.

The reason being, if the power cord is removed from one of the ac feed inlets,
then there the is exposed accessible metal pins of the inlet that must be
double insulated from the other ac feed.

I believe that this scenario is reasonably common, from talking over with our
electrical safety test lab, but the solution of using a single relay as the
changeover element may not be viable.

Please reply directly to me rather to the group as whole unless you feel
there's merit in posting your response.

Thanks.

Best regards,
Bruce Maule


Bruce Maule, Approvals Engineer
Allied Telesyn Research Ltd
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http://www.alliedtelesyn.co.nz/ 



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