Three-Phase Transformer (Two Windings)
Three-phase transformer with variable winding connection.
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Description
If magnetic fluxes are not specified, their initial values are automatically calculated so that the simulation starts in steady-state mode.
The dissipation inductance and the resistance of each winding are set in ohms based on the rated transformer power Pn and the rated winding voltage (V1 or V2).
The two windings of the transformer can be connected as follows:
-
Star
-
Star with neutral
-
Star with earthed neutral
-
Triangle-star (D1), triangle with 30 degrees lag from the star
-
Star triangle (D11), triangle 30 degrees ahead of the star
When star-neutral is selected for the primary winding, an input port labelled N is added to the block. Selecting star-neutral for the secondary adds an additional output port labelled n.
The designations D1 and D11 refer to the conventional clock face, which assumes that the phase of the star reference voltage is at the 12 o’clock position. The reference voltages for connections D1 and D11 are located at 1 o’clock (the triangle is 30 degrees behind the star) and 11 o’clock (the triangle is 30 degrees ahead of the star), respectively.
For more information on the operating modes of a three-phase system connected in a Delta pattern, see Problem solving for delta connection of transformer windings.
Standard designations of winding connections
Two letters followed by a number are used in the designation of a two-winding three-phase transformer. The first letter (Y or D) indicates the star or delta connection of the higher voltage windings. The second letter (y or d) indicates the star or delta connection of the LV windings. An integer from 0 to 12 indicates the position of the positive sequence low voltage reference on the nominal clock face when the positive sequence high voltage reference is at 12 o’clock.
The following three figures show examples of standard winding connections. The dots indicate the polarity signs and the arrows indicate the position of phase A on the primary (HV) and secondary (LV) windings. The phases are assumed to rotate anti-clockwise, so increasing numbers indicate increasing phase shift.
-
Yd1: The LV winding (d) is 30 degrees behind the HV winding (Y). The Winding 2 connection parameters are set to
D1.
-2.png)
-
Dy11: The LV winding (y) is 30 degrees ahead of the HV winding (D). The parameter Winding 1 connection is set to
D1.
-3.png)
-
Dy1: The LV winding (y) is 30 degrees behind the HV winding (D). The Winding 1 connection parameters are set to
D11.
-4.png)
Many other connections with phase shifts from 0 to 360 degrees (in 30 degree increments) can be imagined, combining the phase shift +30 or -30 degrees provided by the block parameters D1 and D11, and in some cases the additional phase shift +/-120 degrees obtained by connecting the triangle winding output terminals to the corresponding mains phases.
The table explains how to set up the block Three-Phase Transformer (Two Windings) to obtain common connections.
| Position on the dial | Phase shift (degrees) | Communication | Primary winding connection | Winding connection 2 | Triangle winding connection to three-phase network |
|---|---|---|---|---|---|
0 |
0 |
Yy0 |
Y |
Y |
- |
Dd0 |
D1 |
D1 |
abc |
||
1 |
-30 |
Yd1 |
Y |
D1 |
abc |
Dy1 |
D11 |
Y |
abc |
||
2 |
-50 |
Dd2 |
D11 |
D1 |
abc |
5 |
-150 |
Yd5 |
Y |
D1 |
bca |
Dy5 |
D11 |
Y |
cab |
||
7 |
+150 |
Yd7 |
Y |
D11 |
cab |
Dy7 |
D1 |
Y |
bca |
||
10 |
+50 |
Dd10 |
D1 |
D11 |
abc |
11 |
+30 |
Yd11 |
Y |
D11 |
abc |
Dy11 |
D1 |
Y |
abc |
For example, to obtain a Yd5 connection, set the Winding 1 connection parameters to Y and Winding 2 connection to D1 and connect the mains phases to the secondary winding as follows:
-5.png)
Setting
Winding 1 connection (~1) - primary winding connection (ABC terminals)
Yg (by default) | Y | Yn | Delta (D1) | Delta (D3)
Primary winding connections.
Winding 2 connection (~2) - secondary winding connection (abc terminals)
Yg (by default) | Y | Yn | Delta (D1) | Delta (D3)
Connection of the secondary winding.
Parameters
Units - system of units
pu (by default) | SI
Specify the units used to enter parameters for this unit. Select pu to use the units. Select SI to use SI units. Changing the Units parameter from pu to SI or from SI to pu automatically converts the parameters displayed in the block mask. Conversion to units is based on the transformer rated power Pn, rated frequency fn and rated voltage Vn in Vrms of the windings.
Nominal power and frequency - rated power and frequency
[250e6 , 50] (By default)
Nominal power and frequency of the transformer.
Dependencies
The nominal parameters have no effect on the transformer model if the Units parameter is set to SI.
Winding 1 parameters - rate of change of current during iRM measurement
[735e3 , 0.002 , 0.08] (by default) | [7.35e+05 4.3218 0.45856]
Nominal phase voltage in volts RMS, resistance and dissipation inductance for the primary winding.
Dependencies
By default [735e3 , 0.002 , 0.08] if the Units parameter is set to pu, and [7.35e+05 4.3218 0.45856] if the Units parameter is set to SI.
Winding 2 parameters - recovery time parameterization
[315e3 , 0.002 , 0.08] (by default) | [3.15e+05 0.7938 0.084225].
Nominal phase voltage in volts RMS, resistance and dissipation inductance for winding 2.
Dependencies
By default [315e3 , 0.002 , 0.08] if the Units parameter is set to pu, and [3.15e+05 0.7938 0.084225] if the Units parameter is set to SI.
Magnetisation resistance Rm - magnetization resistance Rm
500 (by default) | 1.0805e+06.
Magnetisation resistance .
Dependencies
By default 500 if the Units parameter is set to pu, and 1.0805e+06 if the Units parameter is set to SI.
Magnetisation inductance Lm - magnetization inductance Lm
500 (by default) | 2866
Magnetisation inductance for core with non-adjustable resistance.
Dependencies
The parameter Magnetisation inductance is not used if the Saturable core checkbox is selected.
By default, 500 if the Units parameter is set to pu and 2866 if the Units parameter is set to SI.