[Amps] Peter Dahl transformers

[Manfred Mornhinweg]

Mike,

> Why would you want to build a 50V 50A 2500W supply (other than for the
> challenge) when you can buy a HP supply on Ebay for $30-40... 

Very true. The main reason would probably the challenge, and the 
satisfaction of having built your own. There MIGHT be additional 
reasons, though, such as getting a better dynamic regulation than 
typical commercial supplies have, or (specially for hams!) getting an 
extremely low RFI level. Commercial supplies are often tailored to just 
meet FCC specs, and some not even that, while hams usually want ZERO 
detectable noise.

That said, I have to confess that just a few days ago I got in the mail 
a little parcel from China, containing a 13.8 volt, 28.9 ampere 
switching power supply, bought on eBay two weeks before. Sure, I could 
have made my own rather easily - but NEVER at the same price as this 
Chinese product! The price was a tad above 60 dollars, including airmail 
from China to Chile! The parts to build one would have cost me at least 
twice as much.

The quality of this supply is lower than what I would have built myself. 
It does generate some RFI, not much, some parts work pretty hot at full 
power, and its fan is quite noisy. But it works, meets specs, and for 
the application at hand (charging the battery bank of a sailing yacht, 
from a 110 dollar 650W genset), it's fine.

Note that this is a factory new product, not something used and removed 
from somewhere!

> Now, this would be interesting but at the same time I'm swapping all my
> amplifiers out from tubes to BLF578 or MRFE6VP61K25H that need the PSU
> from (1) above...

Much the same here. I just don't see a good reason anymore to develop a 
high voltage supply.

But 50V is too low for many applications. Modern MOSFETs are moving to 
higher voltages. 50V is great for amplifiers in the 100-300W class, but 
larger ones nowadays are better served by supply voltages like 100V, and 
sometimes as high as 300V. These are also optimal voltages in terms of 
easy, efficient and inexpensive switching power supplies!

Manfred

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