# High voltage

Discussion in 'The Projects Forum' started by darshelectro, May 24, 2007.

1. ### darshelectro Thread Starter New Member

Jan 22, 2007
5
0
This is my first time using audio transformers, and i want to make sure i get my calcs correct.

Could you tell me how you would work out what the voltage output on the secondary side will be , if 9 volts from an ac supply was applied on the primary side of the transformer.

More detail:

The 9 volt supply is from a 9volt DC supply. A 555 timer with and transistor on the output will allow the transformer to operate, as the 555 timer will generate square wave. I need a output voltage above 150 Volts and below 230 Volts. I have attached a sample drawing of the circuit.

Below is my calculation:

Primary side:
9 volt supply, resistance 75 ohms, therefore current 0.12 amps.

Is/Ip = (Zp/Zs)^(1/2)

Is= Secondary current, Ip=Primary current , Zp= primary impedance, Zs= Secondary Impedance

Is/Ip = (1200/8)^(1/2)

Is/Ip = 12.2 * Ip

Is= 12.2*0.12 = 1.2 amps

Secondary voltage = (V=I*R) = 1.2* 1 = 1.2 Volts , should be over 150 Volts

The electronic guy has told me that this circuit does produce volt over 150 Volts, as he is away and i am trying to get my head around this, do you know where i have gone wrong?

If so can you correct my mistake?

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2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
Working off the turns ratio, the voltage step-up is 150 (1200/8). With 9 volts driving the primary, that will give you 1350 volts out. For 150 volts, the turns ratio should be more like 16.66.

3. ### pebe AAC Fanatic!

Oct 11, 2004
628
3
Could it be that he has used an output transformer for matching the 1200Ω output impedance of an amplifier to an 8Ω loudspeaker?

If so the transformer will have a turns ratio of 12.2:1

4. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
If that's the case, then the output voltage will be close to 105.