# a look inside an old kocour



## ericrm (Oct 3, 2013)

this is the inside of my old kocour , im trying to figure how its made to see if i could make a bigger version of it... i understand most of what i see but not what could be the big multy plate part? some kind of diode bridge????


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## rusty (Oct 3, 2013)

Selenium Rectifier.


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## ericrm (Oct 3, 2013)

thanks rusty


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## rusty (Oct 3, 2013)

ericrm said:


> thanks rusty



The rheostat on your Kocour adjusts incoming line power to the transformer primary decreasing flux to the secondary coil lowering its output.


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## butcher (Oct 3, 2013)

Looks like an old basic variable DC power supply, a Variac variable transformer, a fixed transformer, rectifier diode (Selenium Rectifier), voltmeter, ammeter,indicator lights switch and wiring.

These can easily be built of most any size, with a basic understanding of electrical and electronics, but you will need to understand how to choose, size, and wire each component, the rectifier (diode) could be a more modern type.





https://www.google.com/search?q=variac+variable+transformer&source=lnms&tbm=isch&sa=X&ei=gI5NUsThGoHViwLLm4HwAw&sqi=2&ved=0CAcQ_AUoAQ&biw=939&bih=563&dpr=1.09


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## ericrm (Oct 3, 2013)

thank butcher, how do i know how much amp a variac can take/ allow to anode ? the one in the kocour is 110v 3A ,and it can do 20 amp in plating solution than i have this one (picture) got it free so i hope to not buy an other one if its maximum rating in solution is suficient...


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## element47.5 (Oct 3, 2013)

What you want to do is to NOT use that device with the selenium rectifier, because when those go bad, they emit highly toxic fumes. Now in the refining world, we deal with fumes that are among the most toxic there are, eg; NO2, and HSe is less toxic but still pretty nasty. 

What you want to do is to buy either an encapsulated bridge rectifier consisting of four diodes, or, 4 individual diodes. I heartily recommend the encapsulated type. You bolt it to a piece of metal for a heatsink. You want about a 25 amp and better, a 35 amp one. About $5-7 buying them one at a time. They look like this:







Enquire further if you need any electrical coaching. There are two connections labeled "~" which is where the AC from the transformer connects. There are two connections labeled "+" and "-" and you are replacing the old selenium deal with this new thing, wire for wire. It's small, about 1-1/2" square, and there's no particular need to remove the old rectifier from the cabinet. Just leave it there, unless it's easy to remove. One machine screw through a hole and it's mounted, done. Nice if you have silicone goop that can conduct the heat, *and helps keep corrosion out*, if you don't, that's probably OK. See if you can buy a little tube of silcone thermal grease for $1 wherever you buy the bridge. Just get a clean interface (sand and steel wool it) between the bottom of the bridge and whatever piece of metal you mount it to, the cabinet or the internal chassis, and have that piece of metal be or large area.


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## ericrm (Oct 3, 2013)

element47.5 lol i love my kocour rectifier and will still use it... but i agree that if there is a risque of poison gaz i will not make one myself with the same dangerous component. do you know how to calculate the variac maximum capacity?

edit : haha i found it:

As such a voltage of 120 with 10 amperes being drawn would equate to 1200 watts which can be shown as 1.2 kiloWatts or 1.2 kVA.

The measure of kVA is specifies the Wattage capacity of a transformer. Any higher Power output (or Voltage input) will cause the transformer to overheat and trip breakers.

if i understand right that mean that the variac would be able to take a maximum of 1200 watts ,or if i understand right 200 A at 6 v ??? right


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## rusty (Oct 3, 2013)

ericrm said:


> element47.5 lol i love my kocour rectifier and will still use it... but i agree that if there is a risque of poison gaz i will not make one myself with the same dangerous component. do you know how to calculate the variac maximum capacity?
> 
> edit : haha i found it:
> 
> ...



Cant help you on the variac but here's a pdf file on selenium rectifiers.


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## element47.5 (Oct 3, 2013)

Ericm you are on the right track. Yes, watts (aka "VA") equals volts times amps. Ergo, if a variac is rated 10 amps at 120 volts, then its capacity is 10 * 120 = 1200 watts or 1200 VA. At 240 volts input, it is good for 5 amps. (I do not know if you are 120 or 240 where you are) 

But you have several items in the chain, and there are also certain other considerations. You also have to take into consideration the capacity of the transformer that the variac feeds. Whatever current your plating tank (or whatever) requires has to pass through that. Additionally, there are various limits on the wattage/VA calculation. For example, you could not supply 1 volt at 1200 amps EVEN IF you had the 1.5" diameter cables required. 

I continue to believe that if you are contemplating building such a device, it is MUCH cheaper to buy a surplus Lambda (or other) power supply. Something like: http://www.ebay.com/itm/7-LAMBDA-Power-Supply-LXS-D-5-OV-/331035896055?pt=LH_DefaultDomain_0&hash=item4d1346e8f7

These go for $5-10-20, this is 5 volts at 27.5 amps. No, you cannot vary the voltage very much, but you can throw 1 or more diodes in series with the output and every diode will drop the volts about .7 volts DC. Diodes (of this current are a buck each if you hunt for them surplus) Put four diodes in series and the output volts will drop 4 * .7 = 2.8 volts for an output of 2.2 volts. 

True, you don't get meters. Look further for "lab" type supplies by Lambda, Kepco, Sorenson. These things are all over the place. 

Keep in mind: Your 10 amp variac alone is maybe $75 used if you buy it a la carte. $120 new. Plus meters. Plus diddling with them to get them to read correctly. Plus the box the thing comes in. The output terminals. The circuit breakers. The big fat knob in the middle. 

Take it from one who builds electronic stuff all the time. If you can buy it surplus, it is massively cheaper and you can get military-grade quality in a nice rack package, which you can then put into ANOTHER cabinet so that corrosion is knocked down.......as long as you don't buy something that got run over by a forklift.


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