On May 7, 2:14*pm, David Nebenzahl 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.