Transformers (3ph, 3 Windings)
Purpose
Three-phase transformers in Ydy and Ydz connection.
Library
Electrical / Transformers
Description

This group of components implements three-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. The primary winding is in star connection with an
accessible neutral point and the secondary winding is in delta connection. Depending
on the chosen component, the tertiary winding is wired either in star (y) or zig-zag
(z) connection.
The phase angle difference between the primary and the secondary side must be
an odd integer multiple of 30
. If the tertiary winding is in star connection the
phase lag against the primary side must be an integer multiple of 60
. If it is in
zig-zag connection, the phase lag can be chosen arbitrarily. The windings of the
secondary and tertiary side are allocated to the transformer legs according to the
phase lags. 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
-
Leakage inductance
- A three-element vector containing the leakage inductance of
the primary side
, the secondary side
and the tertiary side
. The
inductivity is given in henries (H).
-
Winding resistance
- A three-element vector containing the resistance of the
primary winding
, the secondary winding
and the tertiary winding
, in ohms (
).
-
No. of turns
- A three-element vector containing the number of turns of the
primary winding
, the secondary winding
and the tertiary 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
. 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
. The currents are given in amperes (A) and considered
positive if flowing into the transformer. The default is [0 0 0].
-
Initial currents wdg. 3
- A vector containing the initial currents on the tertiary
side
,
and
. The currents are given in amperes (A) and considered
positive if flowing into the transformer. The default is [0 0 0].