"Richard Smith" wrote in message ...

Occasionally day-dream about how I could make a stand-alone rectifier.
Practical advice appreciated.
Less and less need now with inverters getting better and better.
But no inverter I have yet met will run a 6010 "keyholing".

Rich Smith


https://www.electronics-notes.com/ar...-rectifier.php

Start with the welder's maximum current, lets say 300A.
https://www.digikey.com/product-deta...0U60A-ND/80681
The 300UR is reverse polarity. You need two electrically isolated
heatsinks, the positive one for the two diodes whose threaded studs
are cathodes and the negative one for the two that are
anodes. Insulating the four diodes from a single grounded heatsink is
possible but liable to hidden short circuits and the diodes will run
hotter.

https://www.dummies.com/programming/...onents-diodes/

Large finned aluminium heatsinks are common cheap electrical scrap, if
you know where to look. You may have to experiment to find how large a
fan it needs.

The hardest part may be finding and fabricating heat-resistant
electrical insulation that will withstand rough handling. I'd try
unperforated FR4 unclad circuit board material rather than the temping
PVC pipe. The high current terminals can be brass bolts through the
insulation. I've found threaded copper starting motor terminals at a
Diesel electrical shop and lathe-turned them into the high current
studs I needed for a current measuring shunt.

The housing for it can be a welded cube of angle iron with flat sides,
if you don't have equipment to bend sheetmetal. Be sure that at least
one side can be closed without access to the interior, i.e. tapped
instead of clearance holes for the screws.

Calling Jim, and anyone else who can help.

Jim - you said separate the four rectifiers of a bridge rectifier into
two pairs - because of their polarity? If I understand you rightly?

That would mean a practical welding rectifier could have two metallic
heat-sink assemblies separated in a glass-fibre (GRP) frame
(insulating)?

Like the idea...

Should it be air-cooled or oil-cooled?
The one I used (probably 1960's or 1970's vintage) was air-cooled.

Regards,
Rich Smith

"Richard Smith" wrote in message ...


Calling Jim, and anyone else who can help.

Jim - you said separate the four rectifiers of a bridge rectifier into
two pairs - because of their polarity? If I understand you rightly?

That would mean a practical welding rectifier could have two metallic
heat-sink assemblies separated in a glass-fibre (GRP) frame
(insulating)?

Like the idea...

Should it be air-cooled or oil-cooled?
The one I used (probably 1960's or 1970's vintage) was air-cooled.

Regards,
Rich Smith

=================================
Having built a machine that used heat transfer fluid, I wouldn't choose it
for a home project. That machine temperature-cycled GM HEI ignition modules
between [above boiling] and [well below freezing] to confirm that they would
withstand the thermal shocks of for example starting cold and immediately
plowing snow in Alaska. The heatsinks were channels formed on a press brake
from 1/4" copper plate with tubing for the fluid soldered into the inside
corners using large amounts of 95/5 solder.
https://www.eastman.com/Pages/Produc...oduct=71093438

This style of heatsink is convenient to work with:
https://www.bal-group.com/heatsinks/9
For the thermal calculator the power in Watts is the diode voltage drop
times the welding current.

One heatsink is positive, the other negative, so the welding leads can
connect directly to them, which saves fuss and expense of high current
terminal blocks. If instead you choose four identical diodes they need to
mount on four separate heatsinks of the same total size since each diode
conducts half the time. I would enclose the heatsinks in air ducts made of
GRP (FRP here) to confine the air flow within the fins and protect you when
testing it with the external covers off.

An electrically isolated module like this might be a simpler solution if you
have or can machine a flat enough contact surface on the heatsink. It's less
work to build, more to test that it won't overheat and burn out.
https://www.amazon.co.uk/Diode-Bridg.../dp/B07VG1Y3GJ
When I didn't have machine tools available I've fitted an overheating device
to its heatsink by scraping like the old time gunsmiths.

I haven't mentioned methods that require special test equipment like high
voltage insulation testers.
https://www.amazon.com/dp/B00975X2FY..._26725410_item

When I design a home project I determine the essential component specs such
as diode voltage and current, and buy whatever usually surplus parts I find
that meet them. The wiring and mounting details can be worked out later. A
good drill press is essential, a milling machine very helpful.

On Fri, 08 May 2020 10:23:51 +0100, Richard Smith
wrote:

"Richard Smith" wrote in message ...

Occasionally day-dream about how I could make a stand-alone rectifier.
Practical advice appreciated.
Less and less need now with inverters getting better and better.
But no inverter I have yet met will run a 6010 "keyholing".

Rich Smith


https://www.electronics-notes.com/ar...-rectifier.php

Start with the welder's maximum current, lets say 300A.
https://www.digikey.com/product-deta...0U60A-ND/80681
The 300UR is reverse polarity. You need two electrically isolated
heatsinks, the positive one for the two diodes whose threaded studs
are cathodes and the negative one for the two that are
anodes. Insulating the four diodes from a single grounded heatsink is
possible but liable to hidden short circuits and the diodes will run
hotter.

https://www.dummies.com/programming/...onents-diodes/

Large finned aluminium heatsinks are common cheap electrical scrap, if
you know where to look. You may have to experiment to find how large a
fan it needs.

The hardest part may be finding and fabricating heat-resistant
electrical insulation that will withstand rough handling. I'd try
unperforated FR4 unclad circuit board material rather than the temping
PVC pipe. The high current terminals can be brass bolts through the
insulation. I've found threaded copper starting motor terminals at a
Diesel electrical shop and lathe-turned them into the high current
studs I needed for a current measuring shunt.

The housing for it can be a welded cube of angle iron with flat sides,
if you don't have equipment to bend sheetmetal. Be sure that at least
one side can be closed without access to the interior, i.e. tapped
instead of clearance holes for the screws.

Calling Jim, and anyone else who can help.

Jim - you said separate the four rectifiers of a bridge rectifier into
two pairs - because of their polarity? If I understand you rightly?

That would mean a practical welding rectifier could have two metallic
heat-sink assemblies separated in a glass-fibre (GRP) frame
(insulating)?

Like the idea...

Should it be air-cooled or oil-cooled?
The one I used (probably 1960's or 1970's vintage) was air-cooled.

Regards,
Rich Smith
Air cooled should be fine. If you are using silicone diodes the frop
is only about 0.7 volts If you have a 135 amp welder that is only
just over 80 watts dissipation.a few hundred square inches of heat
sink fins can handle that with no problem - particularly with a fan. I
have a set of 600 amp diodes on a finned heatsink of 288 square
inches, more or less. They are a 3/4" stud mount with 3/8" bolt on
"buss bar" type terminals

On 08/05/2020 10:23, Richard Smith wrote:
"Richard Smith" wrote in message ...

Occasionally day-dream about how I could make a stand-alone rectifier.
Practical advice appreciated.
Less and less need now with inverters getting better and better.
But no inverter I have yet met will run a 6010 "keyholing".

Rich Smith

https://www.electronics-notes.com/ar...-rectifier.php

Start with the welder's maximum current, lets say 300A.
https://www.digikey.com/product-deta...0U60A-ND/80681
The 300UR is reverse polarity. You need two electrically isolated
heatsinks, the positive one for the two diodes whose threaded studs
are cathodes and the negative one for the two that are
anodes. Insulating the four diodes from a single grounded heatsink is
possible but liable to hidden short circuits and the diodes will run
hotter.

https://www.dummies.com/programming/...onents-diodes/

Large finned aluminium heatsinks are common cheap electrical scrap, if
you know where to look. You may have to experiment to find how large a
fan it needs.

The hardest part may be finding and fabricating heat-resistant
electrical insulation that will withstand rough handling. I'd try
unperforated FR4 unclad circuit board material rather than the temping
PVC pipe. The high current terminals can be brass bolts through the
insulation. I've found threaded copper starting motor terminals at a
Diesel electrical shop and lathe-turned them into the high current
studs I needed for a current measuring shunt.

The housing for it can be a welded cube of angle iron with flat sides,
if you don't have equipment to bend sheetmetal. Be sure that at least
one side can be closed without access to the interior, i.e. tapped
instead of clearance holes for the screws.
Calling Jim, and anyone else who can help.

Jim - you said separate the four rectifiers of a bridge rectifier into
two pairs - because of their polarity? If I understand you rightly?

That would mean a practical welding rectifier could have two metallic
heat-sink assemblies separated in a glass-fibre (GRP) frame
(insulating)?

Like the idea...

Should it be air-cooled or oil-cooled?
The one I used (probably 1960's or 1970's vintage) was air-cooled.

Regards,
Rich Smith

My Maxarc rectifier unit is air cooled and no fan either, the cooling of
the heatsinks and inductor being by natural convection. I could ask my
mate who has it at the moment to pull to cover and takes some pics if
necessary.

"Clare Snyder" wrote in message
...

Air cooled should be fine. If you are using silicone diodes the frop
is only about 0.7 volts If you have a 135 amp welder that is only
just over 80 watts dissipation.a few hundred square inches of heat
sink fins can handle that with no problem - particularly with a fan. I
have a set of 600 amp diodes on a finned heatsink of 288 square
inches, more or less. They are a 3/4" stud mount with 3/8" bolt on
"buss bar" type terminals

============================

0.7V is a good number to remember for general low power circuits but it's
not strictly accurate. The forward drop is around 0.62V at microamps and it
increases as the logarithm of the current, plus resistively from the bulk
silicon and leads etc. OTOH the drop decreases as they warm up.

The forward drops are as much as 1.65V for these devices:
https://www.huimultd.com/Product/Sol...DK_MDX-series/

This 400A rectifier module is electrically insulated from the heatsink it
mounts on, which can be grounded to simplify construction.
https://www.amazon.co.uk/Single-Brid.../dp/B07VH5BM5B

I didn't find a current rating this high when the thread was active.

"Jim Wilkins" writes:

This 400A rectifier module is electrically insulated from the heatsink
it mounts on, which can be grounded to simplify construction.
https://www.amazon.co.uk/Single-Brid.../dp/B07VH5BM5B

I didn't find a current rating this high when the thread was active.

I can't make out its size, but those terminals don't look huge, and
I'm thinking "Wow is that all that's needed?" (??!!!).
Given the size of a welding cable for 400A ...
Plus the amount of heat one assumes it would have to dissipate (a few
percent of the input power?)
If that allowed you to keyhole with a 6010 from a "tombstone" welding
machine that would be amazing. Given the cost is rather affordable if
it gave that outcome...

Jim - I'll post about welding conditions on s.e.j.w. Bit of science
in there. covid19 lockdown restricting us quite a lot - not welded
for months and getting by as construction site labourer.

"Richard Smith" wrote in message ...

"Jim Wilkins" writes:

This 400A rectifier module is electrically insulated from the heatsink
it mounts on, which can be grounded to simplify construction.
https://www.amazon.co.uk/Single-Brid.../dp/B07VH5BM5B

I didn't find a current rating this high when the thread was active.

I can't make out its size, but those terminals don't look huge, and
I'm thinking "Wow is that all that's needed?" (??!!!).
Given the size of a welding cable for 400A ...
Plus the amount of heat one assumes it would have to dissipate (a few
percent of the input power?)
If that allowed you to keyhole with a 6010 from a "tombstone" welding
machine that would be amazing. Given the cost is rather affordable if
it gave that outcome...

===================================

Using the closest match on an architect's scale the 110mm dimension measures
100 and the pad widths are 17+ and 20, so 19mm and 22mm. The screws just
clamp the cable lugs into contact with the pads. If they are steel they
don't have to conduct much of the current.

If you figure on 1.5V drop per diode the power loss is 1200W, or less if
ITM(?) is the peak forward voltage. For a rough comparison my 1500W electric
heater has a 13 Watt, 5" diameter fan that blows 7(?) MPH at the outer edge.