High amp buck-boost transformer

[hillbilly1]

with today's transformer design software most custom shops, like ours, uses, this is an easy part and takes about 10 minutes to design a custom unit like this one. Most custom xfmr mfgrs for this size unit do not stamp their own steel; it is MUCH cheaper to buy it from a steel scrap supplier who also stamps it or sends it to a stamper for you. With good stock of std E-I & stack core steel, there is seldom any delay to get material. Likewise std cu and al is stocked so seldom any wait for it. Longest time today is dip and oven time. there is seldom any powder coating of parts; if so, the local partner panel shop down the road does it while we build the transformer, so being done in parallel rather than sequentially, again no delay. So 1 week is usually no problem although we do try to get a premium to cover putting it before other customers who were there first. But to get one, one has to ask for a quote first.

Just wondering, how does this affect the listing? Or is it? Usually if something's modified, it has to go through testing again at great cost.

 

[kwired]

Just wondering, how does this affect the listing? Or is it? Usually if something's modified, it has to go through testing again at great cost.

I can't say know the right answer but I could see it being possible to build it to a standard formula - input needed values and build to standards of the formula. Those standards could possibly validate the listing. There is a lot of custom things out there.

Next question is does this item need a listing? Just did a search for the words 'list', 'listed' and 'listing' on my 2008 NEC (CD ROM version) and had no hits in art 450.

 

[mike_kilroy]

Custom listingy

Custom listingy

if one wants UL Listing on a transformer, it must be a certain design and go thru UL destructive testing. Similar for CSA. About a $ 15k cost for one part number, and then yes, it cannot be modified without going thru it all over again.

But xfmrs are most often ok with UL recognition instead. UL visits our xfmr mfgr plant like once per month and verifies the methods and materials used meet UL recognition requirements. It allows placing UR sticker on any xfmr built to the proper specs with UL recognized materials. That also allows CSA equiv stamping for canada with a recripocity agreement. Last I herd this blanket UR thing is like $ 15kyr. Building a UR transformer does not add to its cost.

CE is another story; it can be tested for by a CE testing agency like TUV or some others who specialize in it, or it can self certified. Means by building to CE specs, we can CE label our magnetics by following the rules and saying & documenting that we are following them. We keep a file on each design and part no to back up that it was built to proper specs. CE certification for a whole complex machine is a lot more complex than a single component like a transformer. Building to CE requirements adds typically 15% to the cost of the transformer due to some sorta nonsense spacing and specs that a lot of folks believe add no value to it.

We just designed a new servo 75a power supply that TUV is being payed $ 15k right now doing destructive testing on. Once certified, it cannot be modified w/o the whole process again.