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EFT protection

Respected all,

I am facing some difficulties with my protection circuit of my DCDC converter.I have attached a photo for reference.

my problem is:

1.At very early stage my dc dc converter was getting shut off due to high eft pulse in positive line and the converter output was flickering when eft pulse is applied in negative line.As i found probably as my varistor V175LA20ap clamp voltage is around 400 volt this was causing the shut down of my dcdc converter and the flickering was happening due to the transient created by the diode whenever it was going in reverse mode due to the eft on negative line.(ref my previous circuit drawing of the photo)

2.I have introduce two inductor in differential mode of value 100 uH,hence the high voltage is divided in both the inductor impedance as a result dc dc shutting off problem is gone now but present problem is the dc dc converter output is flickering from lower level eft (1kv,previously it was at 4kv negative eft pulse).What i am doubting is it is causing by the diode so i am planning to replace the diode after the differential inductors and place it just before the dcdc converter.(Ref picture present circuit in photo)

3.But what i am confused is about the capacitor placement between varistor and inductor..As i have studied capacitor have a factor called dv/dt which in turn define the pulse current capability of capacitor.So if i place the cap just after the varistor less current will flow through varistor and a large pulse current will go through the capacitor it may cause some malfunction,spikes also towards the supply.again if i place the capacitor after inductor the i am confused of the back emf of inductor which may not get bypassed by the capacitor and choke the varistor.

So what my confusion is where should i place the capacitor after varistor before diff inductor or after varistor and diff inductor,and what are the reasons to do..