# Rectifier from AC to DC

#### doghuh

Joined Mar 10, 2009
5
Hi,
I really need help. Does anyone knows how to design a circuit to convert 240 VAC to 300VDC??? I need to covert the voltage from the power grid to dc so that i can power a solar inverter without the need of installing the solar panel and connecting it in. Hope to hear from anyone. Will be good if you can attach a drawing. I've been racking my brains for some time.

Thanks
Jeremy

#### b.shahvir

Joined Jan 6, 2009
444
The moment you connect a rectifier directly to the 240VAC mains, the output DC voltage will be equal to the peak value of the AC input voltage.....in this case more than about 300VDC, as the peak value of 240VAC turns out to be approx. about 339VppAC

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#### doghuh

Joined Mar 10, 2009
5
thanks for the reply.
so do u mean i don't need a capacitor or anything. just a rectifier circuit that's all? if so, i only need to connect the ac to a transformer than to a bridge recitifer and connect to a dc output?

#### t_n_k

Joined Mar 6, 2009
5,448
Your inverter may not like having unfiltered rectified AC at its input terminals. Particularly as it normally expects a nice smooth DC from a solar array. You should carefully check the inverter specifications before connecting it to the rectified mains (even with an isolation transformer interposed) - b.shahvir's advice about the peak voltage should be taken seriously. Is 300V the maximum input voltage the inverter expects? If so, then be careful you don't destroy it!

#### thingmaker3

Joined May 16, 2005
5,073
If the "300 V" is the "PV start voltage," then anything from 300V to maximum input will be sufficient to get the inverter running. Do not exceed the maximum input rating. Do indeed use a filter.

If you have any doubt about doing any of this safely, please hire a qualified electrician! Electricians cost a lot less than doctors or morticians.

#### b.shahvir

Joined Jan 6, 2009
444
If you have any doubt about doing any of this safely, please hire a qualified electrician! Electricians cost a lot less than doctors or morticians.
and a lot better than your thread encountering a pre-mature closure!!

#### doghuh

Joined Mar 10, 2009
5
and a lot better than your thread encountering a pre-mature closure!!
y would it close pre-maturely??

Btw, my inverter has a mpp voltage range of 150-400Vdc. That's y i'm trying to cap the circuit at around 300vdc though i know that the rms will reach around 339Vdc. so i'm just leaving an allowance for a surge or anything.

I would really like to hire an electricain. but the sad thing is i'm just a student trying to come up with a circuit to test the inverter for a final year project. so dun have the \$ to do so. lol. I'm actually thinking of coming up with a circuit diagram 1st that's all. only after my lecturer approves the diagram than i can do the circuit. so no worries abt tat.

however, i've yet to come up with the diagram after weeks of going online to search. in fact, i'm still pretty puzzled. so i'm hoping that if anyone of u is kind to show me a sample of the diagram or if can teach me how to do it. or if it's not too inconvient, help me do one.

Thanks for replying though.! really appericaite it.

#### doghuh

Joined Mar 10, 2009
5
oh, sorry sorry. the min mpp voltage is 150, max mpp is 400. the max VDC is 500v

#### b.shahvir

Joined Jan 6, 2009
444
y would it close pre-maturely??
My intention was not to scare you or anything...... but the moderators of this site normally discourage people dabbling with circuits directly powered by 230 Volts or above for safety reasons!

You can always use a suitable Isolation Transformer between the high voltage sections to safeguard yourself against accidental electrocution.

Good Luck!

#### thingmaker3

Joined May 16, 2005
5,073
but the moderators of this site normally discourage people dabbling with circuits directly powered by 230 Volts or above for safety reasons!
If you re-read the closed thread, you will find our objection is to non-isolated mains. And yes, we do encourage people to work with lower voltages first, to get used to technique and precautions. Or to work under supervision, as Doghuh is doing.

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#### thingmaker3

Joined May 16, 2005
5,073
however, i've yet to come up with the diagram after weeks of going online to search. in fact, i'm still pretty puzzled. so i'm hoping that if anyone of u is kind to show me a sample of the diagram or if can teach me how to do it. or if it's not too inconvient, help me do one.
I think the trick here is to create your own diagram. (Unless the class title is "finding other folk's work on the internet.") Post your attempt here and we'll help with suggestions for improvement!

#### doghuh

Joined Mar 10, 2009
5
oh. ok. thanks. totally understand the thing about safety

Anw, this is what i have. A normal rectifier circuit. i dunno how to get the capacitance. But i think the rectifier diodes i'll be using is 1N5404 (3A) it has a peak reverse voltage of 400V and non-repetitive reverse voltage of 525V. Is this enough? can you advice me otherwise?

The fuse i'm planning to use is a 5A or 13A fuse.

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