How to solve Transformer 0-22V ac Flat top in the Sinewave - Reg

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prakashvenugopal

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Hi all,

Transformer Details:

Primary : 0-200-220-240V / 2A

Secondary1 : 24-22-20-0-20-22-24V / 72VA

Secondary2: 0-16.5 / 16.5VA


I had Found Primary Waveform 0-220v ac is Pure sine-wave and Found Flat Topping in the Sine-wave of 0-22Vac Secondary Tx as we attached in the image.

I had measured the current Waveform also and it is attached in the Video for your reference.

Kindly let us know how to avoid this Flat topping in the Transformer Secondary Waveform.

Regards,
V. Prakash
 

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Hi,

Thanks for the reply.

Is there any Single Phase AC/DC using Active PFC to test? Kindly share.

Regards,
V. Prakash
--- Updated ---

crutschow said:
Those harmonics have nothing to do with the quality of the DC out of the regulator.

How is it making you system malfunction?
What does the DC signal look like from the regulator?
Click to expand...
Hi,

I am measuring the THD in the Transformer Secondary using the THD Meter which is showing high when compared to the Transformer Primary and also the Amplifier output Signal is giving noise signal instead of stable signal. DC signal is stable with the +18V DC with 150mV ac ripple and -18V DC with +150mV ac ripple

Regards,
V. Prakash
 
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prakashvenugopal said:
I am measuring the THD in the Transformer Secondary using the THD Meter which is showing high when compared to the Transformer Primary
Click to expand...
Implausible, most likely a wrong measurement. Primary and secondary transformer currents are closely linked.

Seeing 50 Hz and its harmonics in amplifier output is a matter of unsuitable ground layout or possibly unsufficient filtering of preamplifier supply. I presume that 150 mV supply ripple is within your specs. If not clarify with a circuit schematic.
--- Updated ---

If your rectifier circuit involves a transformer center tap, secondary THD will be higher by design.
 
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Hi,

150mV ripple is within the specification only.
I had attached the Powersupply Section circuit for your reference.

Regards,
V. Prakash
 

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  • PowerSupply Section Circuit.jpg
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150 mV ripple after linear regulator is not good. Sure the unregulated DC provides sufficient voltage margin for the regulator? Did you watch it on oscilloscope?

What's the purpose of extra series diodes?
 

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FvM said:
150 mV ripple after linear regulator is not good. Sure the unregulated DC provides sufficient voltage margin for the regulator? Did you watch it on oscilloscope?

What's the purpose of extra series diodes?
Click to expand...
Hi,

I am testing in the Oscilloscope. I have not used the Extra Series diode in the PCB. It is shorted with Jumper.

Regards,
V. Prakash
 

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Can we also assume that the GND is also connected to your transformer center tap ?
 

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