ac - dc convertor.. (a new circuit needed)

i have to convert 230v ac to 12v dc with constant 30 ampere. application is hrc fuse testing for railways. i've a circuit shown below..

i need a simplified circuit..
i want to replace bridge rectifier. we are testing fuses from 1amp to 30 amp range.
so for that we are using 12volt dc input. so to get that dc, i need this convertor. any ideas...?

:smile:
A very simple circuit:
500W 230V/12V-14V transformer
50Amp bridge rectifier
47.000uF/25V electrolytic capacitor

itskannali, that circuit will be hard pressed to supply 1A, let alone 30A. And if you're going to test fuses of amperage from 1 to 30, what you need is a power supply that can stand up to at least 30A, not a constant 30A supply. There's a difference between the two.

If you want a relatively high current capacity like 30A, you can hardly avoid using a bridge rectifier. Sure, you can use a single diode as a half-wave rectifier, but the unbalanced magnetising current on the transformer will be huge. You could also use two diodes in a two-phase full-wave configuration, but that needs a centre-tapped transformer.

How do you plan to test the fuses? By increasing the load current until the fuse blows? Or increasing it to just below the rated current to make sure that it does not blow? Or something else? You must clearly present what you want to do and how so that we can make clear suggestions.

It's hard to make a circuit any simpler than that... you need a rectification stage, and full bridge rectifiers should be fine for that. However, for delivering 30A, the 7812 regulator shown won't do the job.

Do you need the output voltage to be well regulated? If so then you'll need a circuit that's more complicated than the one you posted.

itskannali said:

i have to convert 230v ac to 12v dc with constant 30 ampere. application is hrc fuse testing for railways. i've a circuit shown below..

i need a simplified circuit..
i want to replace bridge rectifier. we are testing fuses from 1amp to 30 amp range.
so for that we are using 12volt dc input. so to get that dc, i need this convertor. any ideas...?

Click to expand...

why do you want to replace bridge rectifier and replace with what?
you can use center tap transformer at the input so that you can tap at different load.
at the output a single 7812 wont work its maximum current is 2.5A you need to add some extra circuitry to get 1-30Amps current

this link can be help full High Current Voltage Regulation - Electric Circuit

the thing is i need to test hrc fuses ranging from 2-30 amps.. need to conduct 3 different tests.... over current, rated, and below rated... input must be 10-12 volt dc... so to get that dc input, i need to make an ac-dc convertor...

If your circuit require about 10-12V/ 30A, you need to use a minimum 400W power supply. That’s the most important detail. You can buy a 12V/40A switching-mode power supply (as the most straightforward way of improving the efficiency) see for example:
TDK LAMBDA|CSS500-12/TI|SMPS, 500W, 12V | Newark.com
or just to use a simple power transformer 230Vac/12Vac (400-500W) + 50Amp bridge rectifier + capacitors.