PLECS Magnetic Domain - Transformer Magnetizing Current

General
1

Hello,

I am trying to model an RM12 transformer I am using to operate a series resonant converter. I have the magnetic circuit in the photo below.

Screenshot 2025-02-19 181359
Screenshot 2025-02-19 181359596×535 14.4 KB

The magnetic seems to work fine, i.e. it consumes the correct amount of current and steps the voltage up accordingly. My issue is that when the rectifying bridge is conducting, I only see the load current passing, while on the input of the transformer you get load current + magnetizing current. It appears that the relationship N1I1 is not equal to N2I2 anymore, as you would expect. Is there a workaround for this? I have already tried to add leakage flux paths, but it didn’t seem to help.

Many thanks for any assistance.

2

This relationship is true only for an ideal transformer without any magnetizing inductance. The MMF for the winding is N*i. Using a reluctance-resistance analogy, with a non-zero reluctance and non-zero flux in the core the MMF of winding 1 and winding 2 will be different, with the difference being due to the “flux flowing through the reluctance”. You can confirm this in a PLECS model.

flux_linkage_demo.plecs (17.7 KB)