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I am designing an AC to DC converter. My power source is a single phase synchronous alternator that has a voltage range of 170~260 VAC and a frequency of 40~60 Hz. Can i use a transformer designed on 50 Hz and 220 VAC to work on my alternator specs mentioned above?

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  • \$\begingroup\$ Depending on where and when it was made, 220 VAC in Europe would require it to have at least 10 % margin on that rating before saturation. You are close though. \$\endgroup\$ – winny Dec 28 '16 at 11:44
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    \$\begingroup\$ Why not use a SMPS, which has input voltage and frequency compensation pretty much built-in? You'll most likely need to get stabilization anyway - it's easier and more efficient to do it on the high side. \$\endgroup\$ – Agent_L Dec 28 '16 at 14:09
  • \$\begingroup\$ How sure you are, that SMPS will handle the range of voltage and frequency i proposed above? \$\endgroup\$ – Mahmoud T. Abuzayed Dec 28 '16 at 18:53
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    \$\begingroup\$ 40 Hz and 260 Vac will most likley put the transformer into deep saturation and blow a fuse/destroy it. You need to keep you voltage*frequency product constant to 50*220 or less at all times. \$\endgroup\$ – winny Dec 30 '16 at 9:01
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    \$\begingroup\$ Sorry, my bad. Not product, ratio. Voltage/frequency ratio. \$\endgroup\$ – winny Dec 30 '16 at 11:15
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Can a 50 Hz, 220 VAC transformer work on 40 Hz, 180VAC?

Yes it probably can - the initial worry is saturation problems due to operating at the lower frequency but, with the voltage dropping to 180 V at 40 Hz, this produces virtually the same magnetization current as 220 V at 50 Hz.

Strictly speaking, if the transformer is nominally rated for 220 V at 50 Hz, you should run it at a nominal voltage of 176 V at 40 Hz.

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    \$\begingroup\$ Can i avoid the saturation by using thicker wire in designing the transformer ? In fact, voltage and frequency both will decrease or increase, change in RPM of the alternator will affect them together. @Andyaka \$\endgroup\$ – Mahmoud T. Abuzayed Dec 28 '16 at 18:38
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    \$\begingroup\$ Saturation current is due to the iron laminates in the core and not the wire thickness. If the volts:hertz ratio remains constant, then you should be OK. \$\endgroup\$ – Andy aka Dec 28 '16 at 18:55
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Be on the safe side by using a transformer designed for heavier load. So the iron loss due to lower frequency can occupy the margin originally designed for heavier load (copper+iron) loss.

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    \$\begingroup\$ Heavier load has nothing to do with it. Decreasing the frequency WILL saturate the core unless the voltage is reduced. Load or no load. \$\endgroup\$ – winny Dec 30 '16 at 8:58
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If you use the mentioned transformer, you will be running the risk that it will overheat when used at 260V, 40Hz. This is because your design requirements are "broader" than the capabilities of the suggested transformer.

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    \$\begingroup\$ Overheating isn't an issue. Saturation is. \$\endgroup\$ – winny Dec 30 '16 at 8:58
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    \$\begingroup\$ The transfomer i inted to use will never work on 260VAC and 40Hz. The power source is a synchronous alternator that its RPM fluctuate between 1300~1800, so it procuces voltage of 170~260 VAC and freq. of 40~60 Hz. Voltage and frequency will increace and decrease together. At 170VAC freq will be 40Hz, and at 260VAC freq will be 60Hz. \$\endgroup\$ – Mahmoud T. Abuzayed Dec 30 '16 at 10:54
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    \$\begingroup\$ @MahmoudT.Abuzayed That relationship is very important and should go in your original question. Please edit it. You will be close to saturation always but it should work. \$\endgroup\$ – winny Dec 30 '16 at 11:14
  • \$\begingroup\$ I hope things will go on without big problems. Thank you for answering :) \$\endgroup\$ – Mahmoud T. Abuzayed Dec 30 '16 at 11:24
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    \$\begingroup\$ With the additional information (that the voltage and frequency "track" each other), I agree with Mahmoud that although you are operating "close to saturation" it should work. \$\endgroup\$ – Guill Dec 31 '16 at 20:52

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