How to define a nonlinear magnetic reluctance in Simscape language?

Hi,

i need some help to define a nonlinear magnetic raluctance in the Simscape language. My task is to build a simulation of an three and five limb transformer with respect to the magnetic paths.

The reluctances should have some saturation and hysteresis to present a real core material. I found a Nonlinear Inductor in the SimElectronic library which is designed with the Jiles-Atherton theory. Nonlinear Inductor

I'm now trying to implement the Jiles-Atherton equations in my own Simscape component.

My first problem is the coth()-function. How can I implement them to work save and don't have critical points?

My second problem is the derivation by H. How can I write a derivation by H instead of time?

Thanks for your help.

Michael