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Irrush current limit before or after rectifier diode bridge

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noisepic

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My circuit including toroid transformer from 220V to 12VAC. I need implement irrush current circuit, but I wonder to implement before toroid transformer or after rectifier diode bridge? which is better.
 

Hi,

How is the rectifier connected to the transformer?
And what does create the high inrush current.

I'm asking because usually the rectifier is connected at the secondary side of the transformer...
But the inrush current often is caused at the primary side of the transformer by core saturation.
If so, then the rectifier isn't involved in the inrush current at all.

Klaus
 

Hello noisepic,
What is the VA rating of the transformer? i.e. Voltage x Current
As stated by Klaus in regards to the inrush current being on the primary side,
you need to determine a value for a slow-blow fuse and a suitable inrush dampening
resistor.
Regards,
Relayer
 

The rectifier connect to secondary side of the transformer. You know that inrush current by charging capacitor after diode bridge, and I want to limit..them.

- - - Updated - - -

Rating 12Vac x30A. I understand that even we dont need irush current if the fuse able to sustain?
 

Hi,

You know that inrush current by charging capacitor after diode bridge, and I want to limit..them.
Click to expand...
Are you sure that the caoacitor charging current is the problem?

Usually - and especially with toroid transformers - the saturation current is the much bigger problem.
A 400VA toroid transformer may easily draw inrush currents >> 50A even with disconnected secondary side.

Do tests:
* measure inrush current without connected load. You need to do this several times, because the current depends on the phase angle at which the power is connected. I recommend at least 10 tests.

There are inrush current limiters. Passive limiters act like NTCs connected in series with the primary winding.

Klaus
 
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    burai

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