300A Rectifier

I am looking for a single phase rectifier with a blocking voltage of at least 30V, current rating of 300A or greater, and a forward voltage of .25V or less. Does anyone know where I could find something like this or if they even exist?

Sam

What are you trying to do? Because no one runs 300A at 30V. You run it at 300V at 30A to reduce the current which reduces the losses.

Is this 300A continuous? Or stall? Because if it's continuous, then what I said above applies. If it's stall, then you need the continuous rating.

SPB16080 & DSS2x110-80A Schottky dual 160 amp. Will not do 0.25 volts!

300U5A, 300U5AMA, 300U5AM 300A 50 VOLT (Vishay IR)
306CNQ200
SPB160100E3 (Microsemi)

I do not see anything that will make the 0.25 volts! At these current levels you should try MOSFETs used as diodes.

IRF2804strl7pp 40 volt 320 amp 1.6mohm (you will need to parallel two to get you forward voltage spec.)

IRF1324S 24V 429A 1mOHM

I am trying to run a high current, low voltage electrode. The 300A is continuous. I have noticed that not many people run at these levels, otherwise this component would be easier to find.

sammyb11 said:

I am trying to run a high current, low voltage electrode. The 300A is continuous. I have noticed that not many people run at these levels, otherwise this component would be easier to find.

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THat tells us absolutely nothing. What are you trying to do? Not how are you trying to do it, but *what*. You may be going about it the wrong way (which is usually the case when someone has seemingly outrageous requirements).

Wild guess: homemade welder?


Torben

Well, yet again he's not got his location filled in, but 300A at 30V is 9000W, three times what you can get from a normal single phase socket in the UK.

Nigel Goodwin said:

Well, yet again he's not got his location filled in, but 300A at 30V is 9000W, three times what you can get from a normal single phase socket in the UK.

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And a few hundred more than you get from a Canadian dryer plug which we use for bigger welders. Maybe he has a big genny.


Torben

30v/300a

You can do it using an active rectifier.

An active rectifier works with power MosFets which you can parallel to obtain the desired current at very minimal losses, well below 0.1V per "diode".

I have experimented with an active bridge rectifier using N and P-channel power MosFets. The circuit worked, but not to my satisfaction. The problem is: N and P-channel MosFets have different RDSON values which makes it almost impossible to obtain a safe rectified voltage. One transistor out of tolerance causes huge shorts switching N and P simultaneously. (just half way is enough for St. Elmo's fire. )

A two-way rectifier doesn't have those problems. The circuit is going to be published in Elektor magazine in July/August 2008.

Give me PM and you might get the circuit in advance.

Best regards

Hans

Why not parallel 3 >100A silicon rectifier diodes?

does active rectifier with mosfet exist in single chip replacing classic bridge diode, i would need approx 50A capacity at 30V?

300a diodes are used in battery chargers for forklift . The batteries I'm referring to are 48 volt and weigh in at about 3,000 lbs, don't remember the a/h capacity..The primaries of the chargers are fused 30a at 480volts.. Not sure of the voltage rating of the diodes either, probably 200 or so. We purchased replacements from the manufacturer, are they were 75 miles down the road from us (Clarklift of Middle Tenn.). I'm sure they weren't cheap either, as none of thier parts were..

What I am trying to do is take 300A at 30V AC and turn it into DC while minimizing voltage drop. I've been told that a gallium rectifier has a forward drop of 0.35V but they are expensive. That could work if I can find one. Another option could be a selenium rectifier. Does anyone know what the forward drop on a selenium rectifier is?

sammyb11 said:

Does anyone know what the forward drop on a selenium rectifier is?

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Seriously old antiques! - and from what I remember the voltage drop is a LOT more than a silicon rectifier - for a 300V rectifer probably 20V to 50V?, so about 10% of that for 30V.

carmusic said:

does active rectifier with mosfet exist in single chip replacing classic bridge diode, i would need approx 50A capacity at 30V?

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Not that I know of, but it certainly is desireable.

sammyb11 said:

I am looking for a single phase rectifier with a blocking voltage of at least 30V, current rating of 300A or greater, and a forward voltage of .25V or less. Does anyone know where I could find something like this or if they even exist?

Sam

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Somehow I don't think you'll be able to find anything with a forward voltage of less than 250mV at 300A, a huge Schottky rectifier maybe?

Hi Sammyb11,

I do not think there are any rectifiers which will meet those requirements.

If i had to meet those requirements, that is a forward resistance of around O.OOO8 ohms
then i would be considering a small sychronous motor running a set of paralleled brushes
on a purpose made commutator.

I personally think that this poster is going about something the wrong way, as Dknguyen
has already mentioned.

Boncuk mentions using power MosFets as surrogate diodes, presumably zero-crossover switching
and driven hard, so as to maximise conductivity.
Boncuk also mentions that this type of arrangement has inherent problems which in his
opinion made it difficult to set up satisfactorily.
However he was referring to a "bridge rectifier assembly", the poster here is looking for
a "single half-wave asembly", such an arrangement may not have the problems that Boncuk
mentioned.
I don't recall what RDSON means, but it may very well not apply to a half wave set up.

Making such an assembly using MosFets, would require at least basic constructor skills
and some understanding of how MosFets work, and how to make and set up the driver circuitry,
and probably use of an oscilloscope when setting up the zero switching.
And it would not be cheap.

Making a sychronous set of brushes is easy to understand, and more could be added to get
the resistance down to an acceptable level.
Most constructors could make such an assembly.

It is dificult to give this poster a reasonable answer which addresses his needs, as he
has only given what he considers to be what he wants for his job.

It is of course possible that Sammyb11 knows exactly what he wants to achieve, and that
a 30 Volt, 300 Ampere, diode with a max forward voltage drop of O.O25 V, is in fact the
most appropriate way to do it.

Best of luck with it, John

Selenium rectifiers have a serious leakage problem, they are also very bulky.
If you are looking at older tech there was a mercury rectifier which could handle very very large currents, they were used to rectify power for trams.

Power Germanium Rectifier? Still probably won't get down to .25V.

Super_voip said:

Selenium rectifiers have a serious leakage problem, they are also very bulky.
If you are looking at older tech there was a mercury rectifier which could handle very very large currents, they were used to rectify power for trams.

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In Victoria there is a cool store called Capital Iron, which has an antiques section in the basement. They have one of these beasts, which together with its mount must be around 2 meter tall. It's a huge glass bulb with various protuberances and some charring from years of use, and they have some documents explaining what it was used for. IIRC this one was used for a subway or tram system like you mentioned.

I'd never even suspected the existence of those things before. That is one impressive bit of kit. I'd *love* to see one powered up. Apparently they are still in use.


Torben