Saturation current of LLC converter primary?

[grizedale]

i am trying to discover what is the saturation current for a primary of an LLC resonant converter.

It is an ETD34 core.

The K value is 0.8.

If the secondary is open, and i measure the primary inductance, then the value that i get is presumably the value that i put into .....

i(sat) = B.A.N/L

where B = 300mT
A = min cross sectional area of core
N = total number of primary turns
L = The inductance vlaue of the primary, measured with the secondary open



you see, i am just wondering that maybe the saturation current is higher when one has a high leakage term?, .........as one does, in an LLC resonant converter

 

[FvM]

I don't understand the purpose of expressing the saturation behaviour of a transformer (with less or more leak inductance) by a saturation current. I would always refer to flux respectively voltage integral.

 

[mtwieg]

Yeah I see what FVM is saying, since it's not primary current that saturates the core, but magnetizing current, which is different, and is derived from the volt-time product (and the number of turns). So just use the normal V*t=B*A*N equation (though instead of using V.t you'll have to make it an integral as FvM implies).

Defining a saturation current only really makes sense for flyback converters, or choke inductors, where the primary current is only magnetizing, not coupled.

 

[grizedale]

if it is Volt.seconds then surely all i need to do is multiply the maximum on time by the maximum voltage across the primary?

 

[FvM]

In other words, the saturation condition for a LLC transformer is basically similar to a non-resonant transformer. Because the LLC circuit can perform a resonant boost operation, I would rather refer to maximum voltage on the secondary side to determine saturation limits.