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Bridge Rectifier out of Diodes ?

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Posted by Omicron on May 8, 2010, 3:50 pm
 


I am currently constructing a Power Supply that needs to have a 250v
40a Bridge Rectifier.  Cant find any Rectifiers the right size....

I know that it can be made from Diodes and can read the Schematic,
but I dont know anything about what kind and size of Diodes to
use......  does anyone have experience with this can give me the right
specs ?

I found a 400v 40a Bridge Rectifier,,,,,,,  can I use this ?

thanks

Posted by Another Dave on May 8, 2010, 3:51 pm
 


On 08/05/2010 16:50, Omicron wrote:


Posted by Ralph Mowery on May 8, 2010, 6:14 pm
 



Yes you can use that one.

For most simple circuits the two main things about diodes is to use the same
or higher voltage and/or current ratings.

You should also know for diodes/bridges of that power rating you have to
bolt them to a heat sink as they will get warm to hot depending on the
actual current that is used.

If you could not find a bridge that is suitable you can build the equivilent
out of 4 diodes.  They should be rated for 250 volts or higher and 40 amps
or higher.  The ones you want will look like small bolts.  They make some
with the same number on them but with an R at the end.  This reverses the
anode and cathode to make it easier to bolt them to a heat sink in the
correct order.



Posted by Josepi on May 8, 2010, 6:35 pm
 

This works, but can get mechanically, a nightmare for a beginner. The
heatsinks usually end up being insulated from the case metal ground and
alive at working voltages, independantly.

The "R" rating can offer a better solution mechanically for the heatsink
arrangements. Insolation mounting kits can be used, also to alleviate this
problem but I would stay away from that. The super thin mica insulation
washers can electrically punch through, and boom, goes your supply.



If you could not find a bridge that is suitable you can build the equivilent
out of 4 diodes.  They should be rated for 250 volts or higher and 40 amps
or higher.  The ones you want will look like small bolts.  They make some
with the same number on them but with an R at the end.  This reverses the
anode and cathode to make it easier to bolt them to a heat sink in the
correct order.




Posted by Josepi on May 8, 2010, 6:30 pm
 

This will depend on your source of voltage you want to rectify. The peak of
your 250vac will be about 353v (x1.414) at your nominal voltage. Any voltage
surges or spikes (dirty power) may exceed the design rating of the
rectifiers.

I would search for a 600volt bridge and also install some despiking
capacitors or MOVs in the circuit ahead of the bridge / diodes to help
prevent flash over problems. Well designed rectification circuits include
these components to avoid mysterious breakdowns.  Again, this depends on
your source of voltage. If wind turbine is you source, you better go much
higher voltage rating, due to surges and dirty power.

Diodes and bridges usually have standard voltage rating jumps 50, 100, 200,
400, 600, 800, 1000v PIV.

For 40amps (if you are rectifying more than a few amperes, you will also ned
to have it heatsinked. ie. Bolted to lots of metal and heat conduction
grease between them (usually silicone lube)



I am currently constructing a Power Supply that needs to have a 250v
40a Bridge Rectifier.  Cant find any Rectifiers the right size....

I know that it can be made from Diodes and can read the Schematic,
but I dont know anything about what kind and size of Diodes to
use......  does anyone have experience with this can give me the right
specs ?

I found a 400v 40a Bridge Rectifier,,,,,,,  can I use this ?

thanks



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