How does a MOT (microwave oven transformer) work

Thread Starter

Cavidex

Joined Feb 19, 2023
28
I'm a newbie to electronics and I found a MOT to turn into the power supply for a high current cell for alkaline water electrolisys, I also bought a bridge rectifier rated at 150A to get the DC power. For the cell I want to use a S.S. steel 316L plate and a galvanized steel plate both 25cmx50cm. I want to maximize efficiency so I want to use all the power that I can. My MOT should be rated at 700W and has a turns to volt ratio of 0.8 ( I already removed the secondary winding) so I will do 7 turns of wire to get around 5 volts and 125 A. Here come's my question: if the cell draws in more power because the electrodes are too big or too close or something else will the transformer output more than 700W (and subsequently more than 150A) and blow my rectifier? ( I live in europe if that helps)(I'm quite young so I can't really buy anything too expensive)
 

Ian0

Joined Aug 7, 2020
10,238
if the cell draws in more power because the electrodes are too big or too close or something else will the transformer output more than 700W (and subsequently more than 150A) and blow my rectifier?
Yes it will, but it is a thermal limit, so you will have enough time to respond before it fails.
I hope you also bought a heatsink. A rectifier will dissipate about 1.5W for every amp.
 

Thread Starter

Cavidex

Joined Feb 19, 2023
28
Yes it will, but it is a thermal limit, so you will have enough time to respond before it fails.
I hope you also bought a heatsink. A rectifier will dissipate about 1.5W for every amp.
I got a Heatsink form an old pc that I found on the street. Is there any way to limit so that it will never draw more than 150A or someway that I can limit the current drawn from the cell like calculating the best spacing between the electrodes? Can I use only one side of the sheets and still use around 150 A?
 

MaxHeadRoom

Joined Jul 18, 2013
28,820
Keep the electrodes filed to the right profile, Preferably use the correct hard copper electodes.
Also don't forget to knock out any magnetic shunt in the TFMR if it has.
It is not the electrode spacing, but the tip area
 

MaxHeadRoom

Joined Jul 18, 2013
28,820
If using standard type point tip electrodes, they usually come supplied with a certain area tip. if used for too long a time, they tend to flatten and consume more current.
 

Reloadron

Joined Jan 15, 2015
7,575
On another note back to the basics. Older microwave oven transformers are easily modified but something you need to consider is wire gauge, especially when we start kicking out numbers like 150 Amps. You need to consider that when rewinding the secondary. Wire gauge is everything.

Ron
 

Thread Starter

Cavidex

Joined Feb 19, 2023
28
On another note back to the basics. Older microwave oven transformers are easily modified but something you need to consider is wire gauge, especially when we start kicking out numbers like 150 Amps. You need to consider that when rewinding the secondary. Wire gauge is everything.

Ron
I already accounted for it and I will buy a 0AWG copper wire
 

Thread Starter

Cavidex

Joined Feb 19, 2023
28
If using standard type point tip electrodes, they usually come supplied with a certain area tip. if used for too long a time, they tend to flatten and consume more current.
for electrodes I'm using 2 steel sheets not meant to be electrodes but they should work
 
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