# 3 phase ac supply to 9v dc

Discussion in 'General Electronics Chat' started by Dimpi, Feb 18, 2014.

1. ### Dimpi Thread Starter Member

Sep 6, 2013
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can anyone suggest me the reference schematic or any guide to how can i make 3 phase ac supply to 9v dc power supply circuit.

i have googled a lot in this but unable to get any idea..help me with any good links that would help in understanding step by step procedure of making power supply from 3 phase ac to 9v dc..

2. ### strantor AAC Fanatic!

Oct 3, 2010
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9v @ how many amps??

3. ### Dimpi Thread Starter Member

Sep 6, 2013
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sir
500 milli amps.

either 9v or 5v ,both will be fine..i thought of using lm7805 to convert 9v to 5v..but if there is any direct power supply circuit which would give me 5V dc from 3 phase supply input.then it would be great..

Last edited: Feb 18, 2014
4. ### strantor AAC Fanatic!

Oct 3, 2010
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What voltage 3 phase?

5. ### Dimpi Thread Starter Member

Sep 6, 2013
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yes sir 3 phase input..
in our country supply is 240V@60Hz..so calculations to be made takin this in to consideration.

Oct 3, 2010
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7. ### Dimpi Thread Starter Member

Sep 6, 2013
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but sir i want to make the design of the power supply..??not use a readymade one..

8. ### strantor AAC Fanatic!

Oct 3, 2010
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Is this for academic exercise or do you hope to save money? Because you cannot make it for less money than you can buy it.

We are not allowed to discuss transformerless power supplies here, so you are looking for a small transformer design. Forget about 3 phase input. You use two legs of the 3 phase, which is a single phase. You can find schematics for this in abundance on google. Transformer>rectifier>caps>regulator.

Oct 3, 2010
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10. ### Dimpi Thread Starter Member

Sep 6, 2013
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sir I am having a smps that gives single phase ac to 9v dc..
m posting u the schematic..may be this helps..now my supply is 3 phase not single phase now is there any cost effective way that this 3 phase be converted to single phase..or something like this..

at first i thought of using half wave 3 phase rectifier but after calculation the voltage at the output of circuit is of large magnitude..so the circuit smps (i posted)couldn't work in that voltage input..it would simply work on 230V rms..

so is there any other suggestion that you would like to share..

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Last edited: Feb 18, 2014
11. ### #12 Expert

Nov 30, 2010
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Suggestion:
1) You don't need 240 V 3 phase power to make 9 volts at half an amp. That's like using a 10 horsepower motor to make an electric tooth brush.
2) If you don't know you can use any 2 wires of the 3 phase power to make a 5 watt power supply, you don't have the skills to design a switch mode power supply.

12. ### Dimpi Thread Starter Member

Sep 6, 2013
96
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sir m not getting you.can you please elaborate??

13. ### R!f@@ AAC Fanatic!

Apr 2, 2009
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Why do you wanna use 3 phase to get just 9V?
How many wires does the 3 phase carry.?
3 wire 3 phase or 4 wire 3 phase ?

14. ### Dimpi Thread Starter Member

Sep 6, 2013
96
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thinking of using 4 wire 3 phase...
is it possible with 3 wire 3 phase??we need to use neutral even isn't it??

15. ### strantor AAC Fanatic!

Oct 3, 2010
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You don't need 3 wire 3 phase or 4 wire 3 phase. #12 already said it well enough, but here's another analogy: Using 3 phases to make a 5W power supply is like using rocket propelled grenade to kill a mosquito.

16. ### R!f@@ AAC Fanatic!

Apr 2, 2009
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I was asking if it is 3 wire then OP cannot use 220V tx.
If it is 4 wire then he can use One phase and neutral and a standard 220V Tx.

17. ### strantor AAC Fanatic!

Oct 3, 2010
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Really? Why is that?

18. ### R!f@@ AAC Fanatic!

Apr 2, 2009
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What is the voltage between 2 phase ?

19. ### alfacliff Well-Known Member

Dec 13, 2013
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just put a three phase bridge rectifier on the smps. it will still function the same after rectification as a single phase or split phase. in fact, you can feed most line operated smps with dc and they will still work.

20. ### tcmtech Well-Known Member

Nov 4, 2013
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Use three 9 volt power packs rated for your three phase input voltages and tie their 9 VDC side outputs together in parallel.

Size accordingly to the amp draw you require.

I take it you have not dealt with our ring tailed mosquitos in North Dakota?

#12 and strantor like this.