Creepage distance of mains transformers AS 3108

Does anyone know off hand the isolation distance between primary and secondary on a EI tranny? i thought it was something like 6mm?

Domestic or light industrial, low to average pollution degree.

Reply to
Geoff C
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"Geoff C"

** Your question is far too vague.

AS3108 gives " Distances through insulation between input and output circuits." ( which applies to a transformer ) as being a little as 0.1mm ( ie 4 thou) for a 250 volt AC supply.

The VA rating of the transformer come into the figure as does the type of insulation used.

How about you ask for the info you are really after?

....... Phil

Reply to
Phil Allison

"Phil Allison" wrote in news: snipped-for-privacy@individual.net:

OK. I do not have access to the standard but will attempt to describe. Transformer is mains and approx 300VA peak, 150VA average with multiple secondaries, elecrostatic screen and 120/120 primary for international voltages. Max secondary winding is 285 volt.

Centre leg 40x73mm, stack height 53 mm. Inter winding insulation is mylar tape, (the yellow stuff) with elephantide type wrap. I am evaluating a new supplier of this tranny and would like to give the go ahead to the manufacturer for an initial run if it is OK. I will do hi-pot testing after I unwrap and check construction. I would like to know the legal requirement for the creepage distance from primary to secondary winding.

Reply to
Geoff C

"Geoff C"

** For a valve amp ??

** Still far to vague.
  1. Is the tranny of "overwound" construction ?
  2. Is there a plastic bobbin ?
  3. Is it intended to meet class 2 requirements ?
  4. Is the mylar layered ?
  5. Is the paper wrap between primary and secondary?

BTW

You seem to think that "creepage" and "clearance " are the SAME as "distance through insulation...."

They are not.

....... Phil

Reply to
Phil Allison

"Phil Allison" wrote in news: snipped-for-privacy@individual.net:

No, measuring equipment.

Yes, overwound, it is not a split bobbin.

Yes

No, earthed equipment

It varies, 2 layers or more mostly. Have not yet measured the thickness.

Yes, 2 wraps.

I am aware of the distinction, and it is creepage I am wanting to know about. ie the distance between pri and sec around the insulators.

Reply to
Geoff C

"Geoff C"

** That ES screen complicates the situation.

Normal creepage and clearance rules go out the window.

Describe it .

........ Phil

Reply to
Phil Allison

"Phil Allison" wrote in news:49tvkgFq8m0dU1 @individual.net:

Yes, I see where you're coming from. Sheet copper, between pri and sec,

2l ayers of mylar tape and a single paper on each side. 40 mm width and centred in bobbin. Layer of paper and mylar tape underneath the end to prevent shorted-turn.
Reply to
Geoff C

"Geoff C"

** Long as that sheet of copper is the same width as the primary winding you have complied.

Often, tranny makers will just wind a singe layer and use that as a ES shield - being careful not to join the ends !

....... Phil

Reply to
Phil Allison

"Phil Allison" wrote in news: snipped-for-privacy@individual.net:

Thanks.

Yep, I've seen the ES as a winding before too.

Reply to
Geoff C

Here

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Buy the standard and all your questions will be answered!

JG

Reply to
Joe G (Home)

"Joe G (Home)"

** That would be the optimist's point of view.

The reality is, you wind up $130 poorer and likely more confused that you ever imagined.

........ Phil

Reply to
Phil Allison

"Joe G \(Home\)" wrote in news:443a3eef$0$7601 $ snipped-for-privacy@news.optusnet.com.au:

I have lots of standards here, but we dont make transformers and have no wish to be experts in the safety requirements, it is not our business. Better to ask of experts sometimes. It takes me a few days to digest a technical standard and I'd rather spend my time elsewhere. (EN61010 is enough for now) Also, it may be years before I need to an autopsy on another tranny. The manufacturer has been told the specs anyway.

Reply to
Geoff C

$130 would be lovely. If it's like most other standards these days, it won't actually give you the information that you need, but will reference 15 other standards, each of which you'll have to buy to painfully extract the few titbits you're after. The standards industry is all about the money these days. Get a bunch of academics and inustry experts to volunteer their time to define the standards, mandate compliance, change it as often as possible, then sell it to all, including the experts who defined it.

Cheers, Alf

Reply to
Alf Katz

Sorry - that was ment to be a sarcastic statement!

You will have more questions after you read the std!

It's understanding the "intent" of the requirement clauses - gives real meaning to the std.... unfortunately std's are like a legal statements - and real meaning is deduced by to those who live and beath the stds applied to their field of expertise.

There are quite a few cases where lab's can have different interpretation of the same std....

JG

Reply to
Joe G (Home)

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