Using LTSpice

LTSpice

1D simulations for electronics

Freely available : www.linear.com

More efficient than co-simulation

Definition by schematics or netlist

Exhaustive library

Applications :

The calculation of components such as capacitances, inductors in electrotechnics or the calculation of stray capacitances, leak inductances or line impedances in QuickField™ leads to fast and accurate results by using LTSpice. For the advanced user, the calculation of thermal parameters in QuickField™ allows the simulations of multi-physics problems.

(LTSpice of Linear Technology)

Inrush current in transformers

LTSpice non-linear iductance is the perfect model

Inrush current analysis at startup

Principle :

According to the help file of LTSpice : "There are two forms of non-linear inductors available in LTspice. One is a behavioral inductance specified with an expression for the flux. The inductor's current is referred to by the keyword "x" in the expression".

Suffice it to use the "table" function, including the data given by the post-processor. This function will give a value of the flux according to the current flowing through the inductance. Which give for instance :

flux=table(x,-45,-49m,-35,-34m,-25,-21.4m,0,0,25,21.4m,35,34m,45,49m)
with -45 = current (I), -49m = flux (Wb), .... The winding resistance is calculated with the AC magnetics module.

Easy postprocessor	Time plot	Simple schematics

Inrush current plot under LTSpice

Spice : parametres d'inductance non linéaire

Parameter of the non-linear inductance model

Behavioural simulation

Parameters calculation for a 1D simulation using LTSpice

Impulse transformer design

Principle :

LTSpice is used to simulate electronical and electrical ciruits, but the magnetic-electric duality allows to design models closer from real behaviour.

Behavioural simulation rely on the use of reluctance for the magnetical part, inductance and resistance for the elctrical part. QuickField™ allows to calculate :

  reluctance (magnetical part) : AC magnetics module

  resistance (winding) : AC magnetics module

  inductance (winding) : AC or DC magnetics module

  coupling coefficient : DC magnetics module

Calculs :

The Transient magnetics module is used with an automatic time step for the currents calculation.

The data plotted on the right pictures show similar results for the secondary output. But on the primary side, the diferences are more important. because QuickField™ is more accurate, as the transient effects can use the geometry of the transformer . Whereas that feature is not possible in a 1D model.

LTSpice : currents in secondary side

QuickField™ : currents in secondary side