Three phase four winding transformer

Three-phase four winding transformer is modeled as three single-phase four winding transformers, meaning that only magnetic coupling between windings of the same phase are taken into account.

The magnetization inductance Lm can be linear or with saturation, it is modeled on the primary side of the transformer. Core losses are modeled as Rm resistance located on the primary side of the transformer. Also, it is possible to neglect Lm and Rm by selecting Lm/Rm neglected in the Core model property. For more informations, please refer to Core model

Schematic symbol and input parameters for three phase three winding transformer block are given in Table 1.

A schematic block diagram of the three-phase three-winding transformer block with the corresponding component arrangement and naming is shown in Figure 1.

It should be noted that terminals N1, N2, N3 and N4 can be connected with the rest of the circuit in schematic editor only if the corresponding side is wye (Y) connected.

Internal variables of the transformer are available for observation at the analog outputs. Names of the variables available for observation have extensions _a, _b and _c added to their names. These extensions correspond to variables of sub circuits of phases a, b and c, respectively.

Table 1. Three phase four winding transformer component in the Schematic Editor core library

component	component dialog window	component parameters
Three phase four winding transformer		Input parameters option (SI or p.u.) Nominal Power of the transformer in VA (Sn) Nominal frequency in Hz (f) Nominal line to line voltage of winding x in volts RMS (Vx, x = 1, 2, 3, 4) Resistance of winding x in ohms (Rx, x = 1, 2, 3, 4) Leakage inductance of winding x in henries (Lx, x = 1, 2, 3, 4) Core model - Linear, Non-Linear, Rm/Lm neglected Resistance representing core losses of the transformer, in ohms (Rm) Magnetization inductance in henries (Lm) Import from PU button
		Winding 1 connection (D or Y) Winding 2 connection (D or Y) Winding 3 connection (D or Y) Winding 4 connection (D or Y) clk_num_12 - determines the phase displacement between voltages of windings 1 and 2 clk_num_13 - determines the phase displacement between voltages of windings 1 and 3 clk_num_14 - determines the phase displacement between voltages of windings 1 and 4
		Embedded coupling 1-2 - inserts a coupling component (Ideal Transformer based or TLM) between winding 1 and 2. Embedded coupling 1-3 - inserts a coupling component (Ideal Transformer based or TLM) between winding 1 and 3. Embedded coupling 1-4 - inserts a coupling component (Ideal Transformer based or TLM) between winding 1 and 4. Type of coupling component - defines whether the inserted coupling component is a core or a device coupling. Device coupling is available only for the Ideal Transformer based coupling. TLM 1-2/Embedded components ratio - Defines how coupling to embedded inductors ratio will be calculated. Related to coupling between winding 1 and 2. Available only for the TLM coupling. TLM 1-3/Embedded components ratio - Defines how coupling to embedded inductors ratio will be calculated. Related to coupling between winding 1 and 3. Available only for the TLM coupling. TLM 1-4/Embedded components ratio - Defines how coupling to embedded inductors ratio will be calculated. Related to coupling between winding 1 and 4. Available only for the TLM coupling. Ratio - Used to specify coupling to embedded inductors ratio if Manual option is selected in TLM/Embedded components ratio property.

Embedded coupling

There are two possible options for embedded coupling in the single phase four winding transformer, Ideal Transformer based coupling and TLM coupling.

If Embedded coupling is set to Ideal Transformer, Ideal Transformer based coupling will be placed between two windings of transformer.

In Figure 2, Figure 3, and Figure 4, respectively, are given visual representations of division of circuit among standard processing cores, in case where Embedded coupling 1-3is set to Ideal Transformer, in case where Embedded coupling 1-2 and Embedded coupling 1-4 are set to Ideal Transformer and in case where all Embedded coupling 1-2, Embedded coupling 1-3 and Embedded coupling 1-4 are set to Ideal Transformer.

If Embedded coupling is set to TLM, secondary winding inductor in the each phase will be replaced with TLM coupling component. Inductance will be divided between coupling and embedded inductors (inductors will be hidden in the TLM). TLM to embedded inductors ratio can be determined by compiler, but also it can be specified explicitly. If Automatic option is selected, ratio will be determined by discretization method. If Manual option is selected, ratio can be explicitly set to meet user requirements. For more information on TLM couplings please refer to Core couplings - TLM.

In Figure 5 and Figure 6, respectively, are given visual representations of division of circuit among standard processing cores, in case where Embedded coupling 1-3 is set to TLM and in case where Embedded coupling 1-2 and Embedded coupling 1-3 are set to TLM.

Analog output signals from three phase four winding transformer