100 amp bridege rectifier

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

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

jsw

The datasheet on that pages states "Surge overload -300~450 amperes peak"

What is the operating current your application needs?

MikeB

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

I LIKE that price. thanks

Karl

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

Sure, if he's going to hot chassis the thing, but hopefully he would know better than that.

Jon

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

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.

^^^^^^^^^^^^

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

Bob

The recommended way to rectify very high currents is with paralleled rectifiers, each having a small series inductor. The inductors don't waste energy, and keep the multiple units at similar currents.

A 50A rectifier will carry 50A average, there's presumably repetitive peaks of (half-wave duty cycle) 140A involved in doing that. So, '100A surge' is just fine with the 50A rated rectifier. Maybe.

The other way to ensure current sharing is to separately fuse all the rectifiers; the small resistance of the fuse is enough to balance them, if you do it right.

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

Hmm ... what voltage do you expect to get out of that rectifier? I calculate about 340 VDC (240 * 1.414).

You're looking in Digikey. They are more focused on the hobby market.

Look at:

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. :-)

Looking through Newark's parts selector, and bearing in mind that you need at least 680 VDC reverse, the closest that I find is:

====================================================================== Manufacturer: POWEREX Newark Part Number: 23H0078 Manufacturer Part No: 1N3295A

RoHS Compliance : Yes Description STANDARD DIODE, 100A, 1KV, DO-8 Diode Type: Standard Recovery Repetitive Reverse Voltage Max, Vrrm: 1kV Forward Current (AV): 100A Forward Voltage Max, VF: 1.5V Forward Surge Current Max, Ifsm: 2.3kA RoHS Compliant: Yes ======================================================================

at a price of $45.90 each. (You will need four, of course.)

There is a major jump in voltage at that current range from

600 V to 1 kV.

If you need that 100A surge for a very short period, you can use lower rated diodes, of course.

No -- you need to put a small resistance in series with each diode, so variations in the forward voltage drop won't cause 90% of the current to be hogged by a single diode.

It is -- as long as you don't expect a bridge rectifier pre-assembled.

Good Luck, DoN.

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.

(skd110,+%22skd+110%22) Make sure to use proper heatsink.

i

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.

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.

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

If you have three phase power , use it. The ripple will be much lower.

Dan