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From: David Nebenzahl on 7 May 2010 17:14
On 5/7/2010 1:24 PM GregS spake thus:

> In article
> <74f52ab7-fc4e-4cc3-870e-237429108826(a)42g2000prb.googlegroups.com>,
> Omicron <omicron89(a)yahoo.com> wrote:
>
>> I need to have a Bridge Rectifier 250V 40a ..... unfortunately
>> there is no such thing available as far as Google can see
>>
>> Can anyone tell me what size Diodes that would work ? I am just a
>> hobbyiost and anything for instructions that I have found, look
>> like they need a College COurse to navigate.
>>
>> Any suggestions or simple equation ?
>
> A bridge only works 1/2 cycle so you would need at least 20 amp
> diodes.

Huh? Where do you get that?

Despite only operating half-cycle, each diode gets the full current
flowing through it, so you need *at least* 40A diodes, better yet 40A.


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)
From: David Nebenzahl on 7 May 2010 17:16
On 5/7/2010 2:14 PM David Nebenzahl spake thus:

> Huh? Where do you get that?
>
> Despite only operating half-cycle, each diode gets the full current
> flowing through it, so you need *at least* 40A diodes, better yet 40A.

I meant to write "better yet *50A*".


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)
From: whit3rd on 7 May 2010 17:24
On May 7, 9:46 am, Omicron <omicro...(a)yahoo.com> wrote:
> I need to have a Bridge Rectifier 250V 40a .....

Huh? That's a device that makes 10,000W of DC
power at relatively high voltage. It's not terribly SAFE
to do that; normal switches and fuses cannot
control such DC power. Is this for a flashing
strobe light to illuminate a stadium?
From: David Nebenzahl on 7 May 2010 17:59
On 5/7/2010 2:24 PM whit3rd spake thus:

> On May 7, 9:46 am, Omicron <omicro...(a)yahoo.com> wrote:
>
>> I need to have a Bridge Rectifier 250V 40a .....
>
> Huh? That's a device that makes 10,000W of DC
> power at relatively high voltage. It's not terribly SAFE
> to do that; normal switches and fuses cannot
> control such DC power. Is this for a flashing
> strobe light to illuminate a stadium?

Hmm; maybe it's for an arc welder. Although I guess those use low
voltage but lotsa current, so maybe not.


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)
From: whit3rd on 7 May 2010 17:59
On May 7, 2:14 pm, David Nebenzahl <nob...(a)but.us.chickens> wrote:
> On 5/7/2010 1:24 PM GregS spake thus:

> > A bridge only works 1/2 cycle so you would need at least 20 amp
> > diodes.
>
> Huh? Where do you get that?
>
> Despite only operating half-cycle, each diode gets the full current
> flowing through it, so you need *at least* 40A diodes, better yet [50A].

No, GregS is right. The rating of rectifiers is on the AVERAGE
current they pass (peaks can be much higher). The voltage
rating, for a bridge, has to be higher than the peak of the AC,
though, because there's a charged capacitor usually on the output.
So, a '250V 40A' bridge is made with 500V 20A rated diodes.
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