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Saturable Transformers

Purpose

Single-phase transformers with two resp. three windings and core saturation

Library

Electrical / Passive Components

Description

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These transformers model two or three coupled windings on the same core.

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The core saturation characteristic is piece-wise linear and is modeled using the Saturable Inductor. The magnetizing current im   and flux Ym   value pairs are referred to the primary side. To model a transformer without saturation enter 1 as the magnetizing current values and the desired magnetizing inductance Lm   as the flux values. A stiff Simulink solver is recommended if the iron losses are not negligible, i.e. Rfe   is not infinite.

In the transformer symbol, the primary side winding is marked with a little circle. The secondary winding is marked with a dot at the outside terminal, the tertiary winding with a dot at the inside terminal.

Parameters

Leakage inductance
A vector containing the leakage inductance of the primary side L
 1  , the secondary side L
 2   and, if applicable, the tertiary side L
 3  . The inductivity is given in henries (H).
Winding resistance
A vector containing the resistance of the primary winding R1  , the secondary winding R2   and, if applicable, the tertiary winding R3  , in ohms (_O_  ).
No. of turns
A vector containing the number of turns of the primary winding n1  , the secondary winding n2   and the tertiary winding n3  , if applicable.
Magnetizing current values
A vector of positive current values in amperes (A) defining the piece-wise linear saturation characteristic of the transformer legs. The current values must be positive and strictly monotonic increasing. At least one value is required.
Magnetizing flux values
A vector of positive flux values in Vs defining the piece-wise linear saturation characteristic. The flux values must be positive and strictly monotonic increasing. The number of flux values must match the number of current values.
Core loss resistance
An equivalent resistance Rfe   representing the iron losses in the transformer core. The value in ohms (_O_  ) is referred to the primary side.
Initial current
A vector containing the initial currents on the primary side i1  , the secondary side i2   and the tertiary side i3  , if applicable. The currents are given in amperes (A) and considered positive if flowing into the transformer at the marked terminals. The default is [0 0 0].