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Old 11th December 2012, 12:28 PM   #71
DF96 is offline DF96  England
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Not a fair comparison. If you push a transformer well away from its nominal resistive load spec you need to derate it. You have not derated enough.

DC was your original point. You have now shifted the goalposts.

Note that in order to get the rectifier heating right the RMS current must be 1.9A. This means that the secondary heating due to ohmic losses will be exactly the same.
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Old 11th December 2012, 01:38 PM   #72
Elvee is offline Elvee  Belgium
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The point of the sim was precisely to make a fair comparison: everything identical, except there is a diode in series with the load meaning the transformer only delivers 100W instead of 200W.
In spite of the reduction, the rms input current almost doubles. We could scale the currents by 50%, the relative gap would remain the same.
If another identical secondary is added with a diode in the opposite direction, everything would be normalized, rms current, waveform, etc. Yet it is twice the non-linear load.

And at no time will there be a DC component in the primary current: this can be seen from the average current in the sim (the few µA's are caused by rounding and sampling errors).

Anyway I give up there: for me, everything that needed to be said has been said
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Old 12th December 2012, 03:42 AM   #73
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I have not read the whole thread but for reducing ac voltage LM317/337 can be used IIRC.

Gajanan Phadte
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Old 12th December 2012, 10:54 AM   #74
DF96 is offline DF96  England
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I think you will find that LM317/337 are for reducing DC voltage.
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Old 12th December 2012, 11:08 AM   #75
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He means this:
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File Type: png ac_317.png (7.9 KB, 15 views)
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