Heavy duty AC to DC converter required

[mche1997]

HI All
I'm looking to see if anyone can supply me or make me an AC to DC converter ?
I had basically searched through the internet and electronics and electrical suppliers looking for a minimum of 16 amp converter from 240vac to 300 or over vdc. It is for running a DC hydrogen generator.

Thanks everyone

[dmills]

35A 600V Bridge rectifier on a heatsink plus a handful of 400V Electrolytics?

Non isolated and crude as fuck but it will give you a NON ISOLATED 300V or so at plenty of current.

300V strikes me as a really weird voltage for electrolytic H2 production, usually a couple of volts at large currents is more like it, after all \$H2^+ + e^-\$ is all about charge not voltage, and the bond strength in H2O is not THAT strong.

Regards, Dan.

[mche1997]

Hi
Thanks for your reply, sorry I didn't mention adding a voltage regular. I tried the bridge rectifier but by adding a regulator as I needed to adjust the voltage for variable gas output, it trips the breaker. A normal angled regulator is not compatible with a bridge rectifier. I don't have really good knowledge on electrical or electronics. The simple solution I found and been told was using an AC to DC converter but a heavy duty one I can find was only available in the US. When the hydrogen generator was hooked up to the bridge rectifier, running at 6 amps, it was showing 260 to 270 vdc from mains. Thats why I needed a converter capable of handling at least 300vdc.

[Ice-Tea]

You haven't mentioned the most important thing yet: budget. But I wouldn't bother cooking up one yourself unless you consider it a learning experience.

Get one of these and call it a day:

http://be.farnell.com/ea-elektro-automatik/ea-ps-8360-10r/power-supply-1ch-360v-15a-adjustable/dp/1607347

[Circlotron]

I tried the bridge rectifier but by adding a regulator as I needed to adjust the voltage for variable gas output, it trips the breaker. A normal angled regulator is not compatible with a bridge rectifier.

When you say an "angled regulator" do you mean a triac phase controller like a light dimmer? Better of using a variac ahead of your bridge rectifier, preferably with an isolation transformer too. Even with the isolation transformer it is still very dangerous. 

[IanMacdonald]

If you use that high a voltage you will get arcing instead of electrolysis. The main product will be steam.

[mche1997]

Thanks for the link, sorry yeh not mentioning the price, very expensive.

[oldway]

How much current your circuit breaker is calibrated for ?

Lets think about the problem: you ask for a dc power of, at least 16A 300V, that means 4.8KW...If your power supply has an eficiency of 100% (what's impossible) and a pure sine current in phase with the mains, the current from the 240Vac mains will be 20A.

To have a perfectly sine current with cos phi =1, you need a Power Factor Correction.
You can't achieve a so low rms current with a simple bridge rectier because the load is not linear.

So, there is no easy solution if your circuit breaker is calibrated for 25A.
With a 40A circuit breaker, the simple solution of a bridge rectifier is possible.

[oldway]

If you use that high a voltage you will get arcing instead of electrolysis. The main product will be steam.

An elementary cell with 25% KOH electrolyte has working voltage between 18V and 2.4V.
Current density is choosen between 0.2 and 0.4 A/cm²
Efficiency vary between 52 and 70%.
Some manufacturers claim their industrial alcaline electrolyser has an efficiency up to 90%

As T.S. says that working voltage of his electrolyser is 240V, it is probably an electrolyser of about 100 cells in serie.

Is that a comercial or a DIY electrolyser ?

Does it produce H2 or Brown's gas? (mixt of H2 + 0.5 O2)

If possible, it would be better for safety to reduce the number of cells in serie and choose a lower voltage not higher than 50V, with several electrolysers in parallel.

Whe don't know if the output voltage of the converter must be isolated or not....for safety, better an isolated output.

[mche1997]

It's a 32a MCB breaker, I tried a 40a bridge rectifier and all works fine but if I add a linear voltage regulator rated at 16a as I would like to adjust the voltage, it just constantly trips the breaker. I was recommended using a variac transformer but its too heavy and bulky to fit into the enclosure.

[mche1997]

Yes, I tried adding a voltage regulator to lower it but it just trips the breaker straight away.
Hard wiring from bridge rectifier to generator works fine, had it running for 40 min several times and its quite cool max at 50 oC, no steam just hydrogen and it even set my carbon monoxide sensor upstairs off.

[mche1997]

Hi

Its a DIY 110 cell plates in series, each plate slightly over 2 volts, produces browns gas. If I reduce the plates, it'll heat up really bad. At the moment its all set-up correctly, running at 6 amps, does not go over 60oC but I need a converter as using a bridge rectifier, adding a voltage regulator would constantly trip the breaker and was told the easiest and cheapest solution is an AC to DC converter.

[oldway]

Ok, it is far more clear now.

Of course, it is a lot of power and you can't solve your problem very cheap.

It is necessary to choose an isolated output....Even so, 300V is a dangerous voltage, I hope you know what you are doing and that you are aware of the dangers of electricity.

First, look for an used isolation transformer 240/240 V of 3 or 4 KVA's....As you use it only 40 minutes, it's enough as power ratings.

Look also for an used transformer 240/48V 800VA.

Connect the secondaries of the two transformers in serie so you add the voltages , and a 40A bridge rectifier.

No need of condensators.

The primary of the 240/240V transformer is directly cnnected to the main's voltage (240V)

The primary of the 240/48V transformer should be controlled by a variac 1KVA 0-240V.
Don't forget to protect the primaries of the transformers by fuses.

Do not use a not isolated power supply, it is far too dangerous.....

NB: if current is not enough, you could add another transformer 240/48V 800VA in serie, with primary directly connected to the mains.
NB2: if you use forced cooling of the transormers (not true for the variac), you can use tranformers of lower power ratings down to max 1/2 the specified power ratings.
NB3: all this at your own risks.....

[oldway]

Industrial applications of Brown's gas :

A lot of informations here:
http://www.spirig.com/index.php?id=53?&L=0

[mche1997]

Hi oldway
How about you making them and i'll buy them off you ?
I'll be needing them in quantities but not huge and regular as I'm not that clued up, just know some basics.
Thanks for your much help.

[james_s]

What kind of voltage regulator are you trying to use on 300V? That's a very high power application, it's not trivial to regulate it.

[oldway]

Hi oldway
How about you making them and i'll buy them off you ?
I'll be needing them in quantities but not huge and regular as I'm not that clued up, just know some basics.
Thanks for your much help.

I am retired and I only repair vintage amplifiers and receivers now....
My workshop is in my little appartement, I already have no more place to live.... 

Look on EBAY or other auction sites.....

[oldway]

What kind of voltage regulator are you trying to use on 300V? That's a very high power application, it's not trivial to regulate it.

No voltage regulation, only a 1KVA variac to adjust the current.

[james_s]

I meant the OP, he said there wasn't room for a variac and that he tried some kind of voltage regulator.

[oldway]

About heating of the electrolyser: the simple ac to dc converter with transformer and bridge rectifier has a high current ripple, that means also that current is DC + AC currents.
Only DC current really produce Brown's gas....AC current increases the heating of the electrolyser....

So, it is possible that it became too hot and that electrolyte begins to boil....

Pure DC will improve the situation but probably not solve it.
You will probably have to cool the electrolyte with a heat exchanger.

[mche1997]

Yes, I will be using a thermal pelter

[oldway]

I meant the OP, he said there wasn't room for a variac and that he tried some kind of voltage regulator.

He was thinking using a variac of 5KVA's controlling all the power....I proposed to use only a 1 KVA variac, controlling only one fift of the power.

[mche1997]

It was just an linear angle 16a voltage regulator bought from RS components

[oldway]

Yes, I will be using a thermal pelter

You means a Peltier element? This is only for low power, you will have to dissipate a power not far from 1 KW....You don't do this with Peltier elements....

[mche1997]

Thank you oldway, I'll try and figure it out, appreciate for your help and all others but anyone knows how to make them, I'll buy it