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How to calculate RC across high voltage windings?

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001:
Hi!

I see RC across high voltage windings (240-400V) at many old gear transformers
Is it sort of "snubber"? How to calculate it?

T3sl4co1l:
R = sqrt(L / Co)
C >= 2.5 Co

Tim

001:

--- Quote from: T3sl4co1l on October 10, 2019, 01:23:53 am ---R = sqrt(L / Co)
C >= 2.5 Co

Tim

--- End quote ---

Thanx a lot!
L and C0 are inductance and capasitance of transformer windings, aren`t they?
Can You tell right words to google more about this?

MagicSmoker:
Co is the stray capacitance of the resonant network you want to dampen and is often difficult to determine, but this article explains a common trick:

https://e2e.ti.com/blogs_/b/powerhouse/archive/2016/05/05/calculate-an-r-c-snubber-in-seven-steps

L is the stray inductance which is the leakage inductance of the transformer, in this case. Anticipating your next question: you can measure leakage inductance on the winding of interest by shorting out all other windings.

Note this approach to RC snubber design is for damping ringing from stray resonant networks. Another common use of an RC snubber across a transformer or a switch - particularly at mains frequency - is to absorb the energy stored in the magnetizing (and leakage) inductance during turn-off. In this case the capacitor is sized so that LI^2 = CV^2 where I is the peak magnetizing current (for the magnetizing inductance) or total current (for leakage inductance) and V is the peak voltage it is permissible to allow the capacitor to charge to.

001:

--- Quote from: MagicSmoker on October 10, 2019, 05:21:11 pm ---  Another common use of an RC snubber across a transformer or a switch - particularly at mains frequency - is to absorb the energy stored in the magnetizing (and leakage) inductance during turn-off. In this case the capacitor is sized so that LI^2 = CV^2 where I is the peak magnetizing current (for the magnetizing inductance) or total current (for leakage inductance) and V is the peak voltage it is permissible to allow the capacitor to charge to.

--- End quote ---

Thanx a lot
It is that I means  :-+

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