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In Reply to: Exceed maximum voltage rating on choke? posted by jdm6457 on September 21, 2006 at 11:59:17:
Is this by any chance a Hammond choke? If it is that 400V DC rating has nothing to do with the voltage rating between the winding and the core (which if I remember correctly is much higher) its their attempt at not publishing the AC rating of the choke.What it means is that for an "average" cap input supply producing 400V DC B+ the choke can handle the AC voltage developed across the choke. It has nothing to due with the insullation and everything to do with the magnetic properties of the choke. The actuall AC voltage across the choke (remember thats NOT the AC voltage coming out of the transformer, or the voltage at the choke pin to ground, but the voltage from one end of the choke to the other) can vary quite a bit depending on the cap values used etc. Before the advent of simulations it was hard to compute the value without actually building the supply, so Hammond chose not to give the AC spec.
I think Hammond had gotten burned too many times by people not understanding what the AC voltage across the choke means, that they just sidestepped it all together and said if you use a cap input filter and keep B+ under 400V you should wind up within the AC range of the choke.
In your application the above means that you should be fine with this choke. I've used one of their "400V" chokes in a 700V supply with no problems what so ever, but I made sure that the AC voltage across the choke was not that large. If you use it in a situation with large AC voltage across the choke (such as in a choke input filter) then they get hot and buzz, not so good.
John S.
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Follow Ups
- Re: Exceed maximum voltage rating on choke? - John Swenson 15:40:22 09/22/06 (1)
- Re: Exceed maximum voltage rating on choke? - jdm6457 21:03:06 09/22/06 (0)
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