2-Winding 3-Phase Transformers
Purpose
Three-phase transformers in Yy, Yd, Yz, Dy, Dd and Dz connection.
Library
3-Phase Transformers
Description





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
lower than the voltage of star or delta windings if the number of turns are
equal.
The core saturation characteristic of the transformer legs is piece-wise linear and is
modeled using the Saturable Inductor. The magnetizing current
and flux
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
as the flux values. A stiff Simulink solver is recommended if the iron
losses are not negligible, i.e.
is not infinite.
Parameters and Dialog Box
-
Leakage inductance
- A two-element vector containing the leakage inductance of
the primary side
and the secondary side
. The inductivity is given in
henries (H).
-
Winding resistance
- A two-element vector containing the resistance of the
primary winding
and the secondary winding
, in ohms (
).
-
No. of turns
- A two-element vector containing the number of turns of the primary
winding
and the secondary winding
.
-
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
representing the iron losses in
the transformer core. The value in ohms (
) 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
,
and, if the winding has a neutral point,
. 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
,
and, if the winding has a neutral point,
. The currents are
given in amperes (A) and considered positive if flowing into the transformer.
The default is [0 0 0].