On Sat, 18 Sep 2010 04:49:22 -0500, "RogerN"
wrote:


"Karl Townsend" wrote in message
.. .
I'm looking to rectify 240 VAC into DC with 100 amp surge capacity.
This will power the servo amps on my Matsuura bedmill. I probably
won't ask as many questions as Iggy about my winter projectVBG

The largest I found is 50 amp:
http://www.digikey.com/scripts/DkSea...me=641-1381-ND

Do I need to come up with some way to put three in parallel? If I do
this do I need to fuse each rectifier?

If a 100 amp unit is out there, my life would be simpler.

Karl

Mains to DC bus is built into most ACVS inverter drives. If you could find
a large, bad, obsolete drive in the trash you would probably have what you
need to get the DC bus voltage. Note this is going to be over 300V DC, be
careful. I've seen a lot of old model drives in the scrap bin at work,
usually from an upgrade to a newer drive.

Also I think you can use an SCR as a rectifier if you connect the control
lead to the correct end. I'm not sure if you need to use a resistor or not,
thought someone here would know more about this.

So, on your ebay search, rectifiers, diodes, SCR's, and drives (obsolete or
bad to be cheap) could do what you need. Sometimes companies stock power
SCR's for their old drives, as drives are obsoleted, their replacement SCR's
can end up on eBay. The newer drives I've worked with usually have IGBT's.

RogerN

!!!!!!!!!

I got a dead 50 hp. old old VFD in a huge cabinet. Its going to have
all the parts I need. I didn't make the connection till just now.

Thanks Roger

Karl

On Sep 18, 12:23*am, Bob Engelhardt wrote:
wrote:
On Fri, 17 Sep 2010 21:33:05 -0400, Bob Engelhardt
wrote:

Wild_Bill wrote:
There are numerous devices to rectify AC to DC at the capacity stated..
The appropriate rectifier arrangement might be ...
*or just a full wave rectifier (2 rectifiers).
* * * * * * * * * * * * * * * * * ^^^^^^^^^^^^

IF he had a center tapped transformer, but he's using 240v "mains" as a
source.

Bob
*If he was in America the 240V "mains" WOULD be center tapped - in
Britain or Europe he needs a FW Bridge.

He is in America, but his center tapped (pole) transformer is 120-0-120,
where he would need a 240-0-240 for a 2 diode full wave rectifier.

Bob

Two diodes will work if he center-taps two series capacitors to
Neutral, . One end will be +150 VDC, the other end -150 VDC.

jsw

"DoN. Nichols" writes:


Look at:

http://www.amazon.com/NTE6114-Hockey-Style-Rectifier-Diode/dp/B00180UVS2

1100 Amp @ 1600 V (I see a $147.50 price *each*, and you would need four
and appropriate heat sinks, and the bolts and preloading spring washers
along with the heat sink compound. (Of course, at a mere 100 A, you
probably would not even get them warm -- but you have to make electrical
connections via the heat sinks. :-)


I've worked with hockey pucks. You MUST use the correct Wakefield clamp;
the contact to the guts within depends on you squeezing it TIGHT; the metal
ends flex with the clamp.

The Wakefield clamp has a strain gauge to tell you if you have it tight
enough.

--
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& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On Fri, 17 Sep 2010 10:47:55 -0700, Jim Wilkins wrote:

No matter how carefully I write operating instructions, the first
person to test them makes a mistake I didn't anticipate. "When I nod
my head you hit it" Now when I say "Press any key to continue" I test
for Alt, Shift and Ctrl, and fake a BSOD with the bell ringing if the
joker hits one of them.

Computers lost the "Any" key some years ago - it used to be the big square
red one on the front of the desktop box. ;-)

Cheers!
Rich

On 9/17/2010 11:00 PM, DoN. Nichols wrote:


Note that is a three-phase rectifier, not single phase. I
suspect that you would need to derate the current rating if you were
using only two thirds of it. At least the 800 V rating is sufficient
for the PRV you would encounter.

Enjoy,
DoN.


I had made the assumption that Karl would want to use three phase, since
he has it and will want to keep his capacitance as low as possible.

Kevin Gallimore

On Sep 18, 5:27*pm, Rich Grise wrote:
On Fri, 17 Sep 2010 10:47:55 -0700, Jim Wilkins wrote:
...
Computers lost the "Any" key some years ago - it used to be the big square
red one on the front of the desktop box. ;-)

Rich

On the machines I've wired up recently that's the emergency KILL
button. Usually it's shaped like a mushroom.

Just for you, Press Every Key to Continue.

jsw

I'd use an isolation transformer and not put rectifiers on the mains.
Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
"Our Republic and the Press will Rise or Fall Together": Joseph Pulitzer
TSRA: Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Originator & Charter Founder
IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com/

On 9/17/2010 11:23 PM, Bob Engelhardt wrote:
wrote:
On Fri, 17 Sep 2010 21:33:05 -0400, Bob Engelhardt
wrote:

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

IF he had a center tapped transformer, but he's using 240v "mains" as a source.

Bob
If he was in America the 240V "mains" WOULD be center tapped - in
Britain or Europe he needs a FW Bridge.

He is in America, but his center tapped (pole) transformer is 120-0-120, where
he would need a 240-0-240 for a 2 diode full wave rectifier.

Bob

"Martin H. Eastburn" wrote:

I'd use an isolation transformer and not put rectifiers on the mains.


But they shine a very pretty blue when lightning hits! ;-)


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.