100 amp bridege rectifier

On Fri, 17 Sep 2010 08:20:27 -0500, Karl Townsend

http://www.galco.com/scripts/cgiip.exe/wa/wcat/itemdtl.r?listtype Êtalog&pnum=M50100SB600-CRDM
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On Fri, 17 Sep 2010 12:07:44 -0500, Don Foreman

BINGO!!
I like this better than four diodes. I wasn't going to ground DC- and my plan was to connect direct to 240 through a contactor and fuse. I see I should look at resistors in front of my caps. I'll look into this and probably ask for confirmation.
Karl
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My formula for cap size:
Smoothing capacitor for 10% ripple, C = (5 × Io) /( Vs × f) C = smoothing capacitance in farads (F) Io = output current from the supply in amps (A) Vs = supply voltage in volts (V), this is the peak value of the unsmoothed DC f = frequency of the AC supply in hertz (Hz), 50Hz in the UK
C= (5*50)/(400*60) C=.01 farad or 10,000 MFD
I haven't found anything for a resistor to keep a huge amp surge right at startup under control. Should i just get something like a 2 ohm ceramic tube resistor?
Karl
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Karl Townsend wrote:

Reading the data sheet for that product, it will handle a 100A surge for a little less than one second; the 50A rating refers to the maximum average current.
If your 100A surge is limited in duration, that product might work just fine.
Jon
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On Sep 17, 1:58 pm, "Jon Danniken"

If this circuit really does rectify the AC power line the instantaneous fault current is somewhere over 5000A. This is no place to push the component specs.
jsw
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Jim Wilkins wrote:

OP stated he needed a component to satisfy the demands of a 100A surge. According to the specifications, as I specified in a reply which was longer than the short section which you quoted above, the part he suggested might work, depending upon the duration of the 100A surge.
As to a 5000A surge, that was not mentioned by the OP as a design criteria.
Jon
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On Sep 17, 6:07 pm, "Jon Danniken"

It's not part of the intended use, it's what you get if a diode fails short, before the breaker responds.
jsw
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Jim Wilkins wrote:

Sure, if he's going to hot chassis the thing, but hopefully he would know better than that.
Jon
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On Sep 17, 7:43 pm, "Jon Danniken"

The fault current path is through the shorted diode and the forward biased one connected to the other AC line, IOW right across the pole transformer.
jsw
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On Fri, 17 Sep 2010 15:07:40 -0700, "Jon Danniken"

Put a big inductor on the load. It will limit the power surge without wasting any DC power. Make sure the rectifier is rated for at least 3 times the operating RMS voltage if using an inductor or inductive load.
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On 9/17/2010 9:20 AM, Karl Townsend wrote:

http://theelectrostore.com/shopsite_sc/store/html/sk95d08-new.html
Close enough?
Kevin Gallimore
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On Fri, 17 Sep 2010 17:41:48 -0400, axolotl

I LIKE that price. thanks
Karl
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wrote:

Please remember that the DC+ and DC- lines are still connected to AC HOT and anything that they attach to must be isolated from all other circuits.
jsw
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[ ... ]

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.
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If you have three phase power , use it. The ripple will be much lower.
Dan
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On 9/17/2010 11:00 PM, DoN. Nichols wrote:

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
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On 9/17/2010 9:20 AM, Karl Townsend wrote:

The datasheet on that pages states "Surge overload -300~450 amperes peak"
What is the operating current your application needs?
MikeB
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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.
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.
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"Karl Townsend" < snipped-for-privacy@embarqmail.com> wrote in message
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Wild_Bill wrote:

^^^^^^^^^^^^
IF he had a center tapped transformer, but he's using 240v "mains" as a source.
Bob
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On Fri, 17 Sep 2010 21:18:54 -0400, "Wild_Bill"

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??

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