Bryan wrote:
Paul E. Cater wrote:
------A total SNIP of everything and on to a better idea.-------


Consider using avalanche rectifiers and it makes all the stuff about the
caps and resistors a mute point. There are some good application notes
out there on this subject and the whys and wherefores of it all.

For your needs the BYM36E might be a good choice. At around 30 cents a
piece hard to beat.


http://www.alliedelec.com/Search/Sea...61EC8009E6617F
Best of luck in your project!

Regards,
Paul


GregS wrote:
I am having some difficulty finding a bridge rectifier of 3 Kv and 3
amps.
??

thanks
greg
N6GS

I perused the datasheets of both the BYM36E and 1N5408. Of the
specifications that could matter (that differed):

Reverse Current:
1N5408 = 5uA @ 25°C Ta, 500uA @ 100°C Ta
BYM36E = 5uA @ 25°C Tj, 100uA @ 150°C Tj

Reverse Recovery Time:
1N5408 = Not Rated
BYM36E = 150ns

Nonrepetitive Peak Forward Surge Current:
1N5408 = 200A
BYM36E = 65A

While the BYM36E shows better Reverse Current figures at elevated
temperature (and the measurement point isn't the same), I think it unlikely
that the OP is going to operate them at such temperatures. Considering the
application is 50/60Hz (Period = 20/16.6 ms), Reverse Recovery Time is not a
factor. However, when it comes to Nonrepetitive Peak Forward Surge Current,
the 1N5408 is clearly better. Allied shows 23 hits for 1N5408, the least
expensive being $0.092 each in 1-24 piece lots (stk #568-0554).

Bryan



Good day all,

There are other factors that make avalanche rectifiers a good choice
over standard types. Of course he should not exceed the specifications
on the data sheets for either. Comparing apples to oranges here and
overlooking the advantages of the basic behaviors of an avalanche device
in an application that can be plagued with spikes.

Here is a couple references on the subject. There are many more out and
about.

http://www.dynexsemi.com/assets/DNX_AN5370_Jul02.pdf

http://www.highvoltageconnection.com...che-diodes.htm


The "non-snappy" behavior, minimizes circuit ringing and can reduce RFI
too! They are rugged and able to withstand reverse energy much better
than conventional diodes.

If the OP was actually thinking of using resistors and caps as has been
batted around relentlessly in this group and others, and when compared
to other avalanche class devices, the .30 cents is a good price.

I have no doubt that if he decides to slap in 5408's with or without all
the extra stuff, it will give him years of service taking for granted he
has the PIV and "I" requirements properly. I simply wanted to offer him
an alternative that eliminates the compensation network argument and
adds another layer of protection.

Best regards to all,
Paul
WD8OSU









It is up to him as to how he wants to approach and remedy his situation.
He is the engineer on the project.