On Fri, 17 Sep 2010 21:18:54 -0400, "Wild_Bill"
wrote:

There are numerous devices to rectify AC to DC at the capacity stated. The
appropriate rectifier arrangement might be full wave bridge rectifier ( 4
rectifiers), or just a full wave rectifier (2 rectifiers).

Packages are available with dual rectifiers ( 3 terminals) arranged in
common cathode or common anode configurations, with heat conducting mounting
surfaces.

Stud rectifiers don't usually get threaded into the material they're mounted
to, I dunno where that fairly common thought came from.. Uhm, looks like a
bolt, it must screw into a threaded hole, then.
Instead, they're generally mounted with proper insulators (to provide
isolation) to a heatsink material with hardware (often included parts such
as mica disc and plastic insulating shoulder washers, crimp or solder tab
ring terminal and a hex nut).
The required hole sizes and precautions are stated in the installation
instructions, sometimes included in the device datasheet.

You'd be very surprised at how many applications use the stud mount as
teh terminal as well as the heat transfer point - bolting directly to
the heat sink. Why ele would they be produced as both positive case
and negative case devices??


The mica disc washer allows thermal conduction from the rectifier base to
the heatsink.
The plastic shoulder washer provides additional electrical insulation
between the stud and heatsink.

With the proper insulating parts in place, the heatsink isn't tied to the
anode or cathode of the rectifiers. The heatsink should then be tied to
earth ground.

When installed without insulating parts, the heatsink becomes a conductor in
the circuit, and must be electrically isolated from chassis and/or earth
ground.

For fabricating a FW bridge rectifier with 4 stud rectifiers, it's often
desirable to utilize 2 pairs of opposite polarity terminals.

An equivalent FW bridge rectifier can be fabricated with 2 dual rectifier
packages.

A replacement guide such as NTE/ECG components will have selection charts
and required information regarding the use of industrial rectifiers with
various electrical and physical characteristics.
Basic application specifications are also included.

BTW, proper protection for the 240VAC side would provide 2-pole
interruption, unlike just one hot line connection for 120VAC.

PROPER protection would be a 2 pole contactor with a crowbar at that
current and voltage level.