# how to change the frequency of supply ????

Discussion in 'The Projects Forum' started by lesin akbar, Dec 16, 2007.

1. ### lesin akbar Thread Starter Active Member

Dec 16, 2007
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can any one help me in solving out this thing ? I need to change the frequency of the 230v ac power supply using the microcontroller(89c51). and what if the load takes high current ? which is the best method ?

2. ### Papabravo Expert

Feb 24, 2006
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1,850
If your little friends told this was possible on the cheap then they were wrong. The only way I can see this happening is to use a motor coupled to a generator that will produce the correct output.

3. ### lesin akbar Thread Starter Active Member

Dec 16, 2007
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i just had this thought because i thought of the thing which we do with lower power. ie first to bring ac to dc(after stepping down) then use an oscillator for the desired freqency.

4. ### recca02 Senior Member

Apr 2, 2007
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that is the principle used in Variable frequency drives.
try a google search on those and inverters,IGBT etc.
first the ac is rectified and then a desired frequency of output ac is obtained by controlling the firing rate of the IGBT/mosfet etc.

5. ### cumesoftware Senior Member

Apr 27, 2007
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No. Explanation below.

It is indeed possible to do that. Computer PSUs work that way. The current is first converted to DC and then pulse modulated to feed a high frequency transformer. the advantage of doing this is that high frequency transformers are smaller that 50Hz ones with the same VA rating.

Indeed.

6. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
I forgot to mention that my assumption was that with a sine wave in he would want a sine wave out. The AC-DC-AC conversion doesn't produce a sine wave out -- does it?

That is why I suggested the motor generator combination.

7. ### cumesoftware Senior Member

Apr 27, 2007
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It is still possible to produce a sine wave using a signal generator. Although a motor generator combination might be simpler to implement.

8. ### lesin akbar Thread Starter Active Member

Dec 16, 2007
30
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yes i think the pulse generated will be smoothen by passing thru an induction coil.

9. ### cumesoftware Senior Member

Apr 27, 2007
1,330
11
I don't think it will be a sine wave, though.