Re: OT: Bridge Rectifiers

["Bob La Londe" <onebikenut@xxxxxxxxx>]

"Jim Rojas" <jrojas@xxxxxxxxxxxx> wrote in message
news:PkFWo.34367$sx4.18943@xxxxxxxxxxxxxxx
> Bob La Londe wrote:
>> I am working retrofitting a control system (hobby stuff - (industrial
>> hobby)) and I was considering reusing some of the components. One of the
>> things is a 230-60V transformer that feeds into a modularized bridge
>> rectifier to produce 84VDC under load. The transformer is fine, the caps
>> (BIG caps) need to be tested, but I was wondering if the diodes in the
>> rectifier have a predictable service life? I can make my own easily
>> enough with a handful of heavy diodes, but I really like the neat
>> packaging of this modular one. One less thing to have to bread board.
>> This is NOT a low current application.
>>
>>
>
> Predictable? No. As long as the rectifier is rated 25+ percent higher than
> the actual load, you should expect a long life.

20 years?  50 years?  This system is 26 years old.  I do not know how much
use it actually saw, but it was not a cheap system in its day.  I imagine it
saw some.  It was well beyond the price range of even the most dedicated
hobbiests in 1984.  Are you saying basically that if it works fine now under
the load I plan to use, has a suitable safety margin, and doesn't get hot it
should be fine for an indefinite period?

> High heat is what kills them. So if your rectifier is rated at 100A, Try
> not to push anymore than 75A through it. You can also put rectifiers in
> parallel. Since they are sharing the same AC input, they are automatically
> in phase. This will greatly reduce the heat generated.

Not a bad idea.  There are a couple salvageable modular rectifiers that look
the same as this one in the control cabinet, and one that is bread boarded
for the lower voltage stuff.

Thanks Jim.