PLECS 2.1 Online Help

2-Winding 3-Phase Transformers

Purpose

Three-phase transformers in Yy, Yd, Yz, Dy, Dd and Dz connection.

Library

3-Phase Transformers

Description

pict
pict
pict
pict
pict
pict

This group of components implements two-winding, three-phase transformers with a three-leg or five-leg core. The transformer core is assumed symmetrical, i.e. all phases have the same parameters. Depending on the chosen component , the windings are wired in star (Y) or delta (D) connection on the primary side. On the secondary side, the windings are either in star (y), delta (d) or zig-zag (z) connection. Star and zig-zag windings have an accessible neutral point.

The phase angle difference between the primary and the secondary side can be chosen. For Yy and Dd connections, the phase lag must be an integer multiple of 60∘ . For Yd and Dy connections the phase lag must be an odd integer multiple of 30∘ . The phase lag of zig-zag windings can be chosen arbitrarily. The windings of the secondary side are allocated to the transformer legs according to the phase lag. Please note that the phase-to-phase voltage of delta windings is by a factor of   √ -
1∕  3   lower than the voltage of star or delta windings if the number of turns are equal.

pict

The core saturation characteristic of the transformer legs is piece-wise linear. 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.

Parameters and Dialog Box

[Picture]

Leakage inductance
A two-element vector containing the leakage inductance of the primary side L1   and the secondary side L2  . The inductivity is given in henries (H).
Winding resistance
A two-element vector containing the resistance of the primary winding R1   and the secondary winding R2  , in ohms (_O_  ).
No. of turns
A two-element vector containing the number of turns of the primary winding n1   and the secondary winding n2  .
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.
No. of core legs
The number of legs of the transformer core. This value may either be 3 or 5.
Phase lag of secondary side
The phase angle between the primary side and the secondary side, in degrees. Unless the secondary side is in zig-zag connection, the angle can only be varied in steps of 60∘ .
Initial currents wdg. 1
A vector containing the initial currents on the primary side i1,a  , i1,b   and, if the winding has a neutral point, i1,c  . The currents are given in amperes (A) and considered positive if flowing into the transformer. The default is [0 0 0].
Initial currents wdg. 2
A vector containing the initial currents on the secondary side i2,a  , i2,b   and, if the winding has a neutral point, i2,c  . The currents are given in amperes (A) and considered positive if flowing into the transformer. The default is [0 0 0].