Re: [CAD_CAM_EDM_DRO] blown rectifier bridge question

docholliday02743 wrote:

>Help! I am assembling my control box and have installed and wired the
>fans and the toroid primary. I gently secured the rectifier bridge
>(from mouser, 25 amp 600v) I wired the 55vac to the a/c side of the
>rectifier and was going to read the d/c voltage at the d/c terminals
>before hooking anything up (capacitor, etc..) instand loud hum and
>shorted rectifier bridge! measured resistance across a/c terminals of
>rectifier after this and it is shorted (0.2 ohms). Figured bad bridge,
>installed 2nd bridge (this time testing resistance prior to hooking
>up, and instant short again. It isn't the secondary of the trans as
>that tests fine and there is no short if I plug in the primary from
>the trans and leave the secondary not connected to anything- good a/c
>output and no short. I am wondering if the capacitor MUST be installed
>before hooking up power?
>
>

Either these rectifiers are not rated as you expect, or you are hooking them
up wrong. Does your DVM have a diode test function? You should verify
that the diodes are really hooked up as you think before powering it up
again. Wiring a light bulb in series somewhere should save any more
fireworks
until you have the connection right. You will NOT need the capacitor
connected
to prevent damage like this.

Jon