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What are the long term effects of operating a transformer in Saturation mode? Let's say my transformer can deliver 1VA of power while operating in saturation mode and i consume around 0.6-0.7 VA. Would a long term use (>3 years) of transformer in saturation mode can potentially damage the transformer (it's core or any other part?) when we are operating a const 70% of it's total capacity?

If yes, how can i alter the design (increase it's power capacity?) so that my transformer does not breakdown in long term usage while in saturation mode.

i understand operating in saturation mode can potentially distort sine wave, but it does not matter to my application. i have searched this form but could not find an answer.

Thanks.

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When the magnetizing curve goes above the knee point of saturation, then the inductance is reduced to the air core inductor. Therefore with absence of reactance the impedance of the transforemer becomes only the resistance of the winding. In such scenario for short time the transformer acts like short circuited. It is now regarding the mains impedance how much current it will flow from mains. In domestic network the xformer will heat up without any big noticable fact, while in industrial network it will blow the fuse, since the mains impedance is lower. The xformer in saturation condition will excessively heat, this is the effect.

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  • \$\begingroup\$ i kept it operating for >72 hours and there was no noticeable heating effect at all. So does it mean that it will work? Why do you propose that it will below the fuse in industrial network but work in domestic load? \$\endgroup\$ – Bhavneet Singh Bajwa Jun 6 '16 at 10:50
  • \$\begingroup\$ @BhavneetSinghBajwa Becuse the domestic network has a larger impedance than the industrial. I=U/Z. \$\endgroup\$ – Marko Buršič Jun 6 '16 at 12:06
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There two primary effects that you will be concerned with (you mention you don't care about harmonics and distortion so I won't cover that).

For long term use you're going to want to understand how much additional heat is being generated and how that might adversely affect your operational range and longevity.

A more subtle effect is what impact is this saturation will have of noise performance. In some very high performance ceramics you can see "field popping" at saturation. Once the level for saturation is reached the magnetic field rapidly expands outside of the core and can involve other circuits and induce currents in secondary structures. It can have a noticeable effect on EMI/RFI performance and compliance. (Having been burned by this is a poorly design switch mode supply - I can advise you it can be hard to find)

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  • \$\begingroup\$ The max. output current that i have recorded for the Transformer is 0.05 amps and the max input current that i have recorded is around 0.12 amps. For such low power consumption (~0.5VA) do i still need to worry about "field popping"? \$\endgroup\$ – Bhavneet Singh Bajwa Jun 6 '16 at 11:04
  • \$\begingroup\$ @BhavneetSinghBajwa you've asked a general question, I've provided a general answer so you can then go and investigate further for yourself. There is almost no detail in your question so the answer will be " I don't know" \$\endgroup\$ – placeholder Jun 6 '16 at 14:45
  • \$\begingroup\$ The transformer is a step down transformer: 60 to 12 volts, 0.05 amps consumed at output. Iron (CRNO) Core. What more information can i provide so that you can guide me better? \$\endgroup\$ – Bhavneet Singh Bajwa Jun 7 '16 at 6:53

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