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Multi-Winding Transformer

Implement multi-winding transformer with taps

Library

Fundamental Blocks/Elements

Description

The Multi-Winding Transformer block implements a transformer where the number of windings can be specified for both the primary (left side windings) and the secondary (right side windings).

The equivalent circuit of the Multi-Winding Transformer block is similar to the one of the Linear Transformer blocks and the saturation characteristic of the core can be specified or not. See the Saturable Transformer block reference pages for more details on how the saturation and the hysteresis characteristic are implemented.

The equivalent circuit of a Multi-Windings Transformer block with two primary windings and three secondary windings is shown in the next figure.

You can add equally spaced taps to the first primary winding (the upper-left winding) or to the first secondary winding (the upper-right winding). The equivalent circuit of a Multi-Winding Transformer block with one primary winding and eight taps on the first of the two secondary windings is shown in the next figure.

The winding terminals are identified by the corresponding winding number. The first winding is the first one on the primary side (upper-left side) and the last winding is the last one on the secondary side (bottom-right side). The polarities of the windings are defined by a plus sign.

The tap terminals are identified by their winding number followed by a dot character and the tap number. Taps are equally spaced so that voltage appearing at no load between two consecutive taps is equal to the total voltage of the winding divided by (number of taps +1). The total winding resistance and leakage inductance of a tapped winding is equally distributed along the taps.

Parameters

Configuration Tab

Number of windings on left side

Specifies the number of windings on the primary side (left side) of the transformer. Default is 1.

Number of windings on right side

Specifies the number of windings on the secondary side (right side) of the transformer. Default is 3.

Tapped winding

Select no taps (default) if you don't want to add taps to the transformer. Select taps on upper left winding to add taps to the first winding on the primary side of the transformer. Select taps on upper right winding to add taps to the secondary winding on the right side of the transformer. The number of taps is specified by the Number of taps (equally spaced) parameter.

Number of taps (equally spaced)

This parameter is not enabled if the Tapped winding parameter is set to no taps. Default is 2.

If theTapped winding parameter is set to taps on upper left winding, you specify the number of taps to add to the first winding on the left side.

If theTapped winding parameter is set to taps on upper right winding, you specify the number of taps to add to the first winding on the right side.

Saturable core

If selected, implements a saturable transformer. See also the Saturation characteristic parameter on the Parameters tab. Default is cleared.

Simulate hysteresis

Select to model hysteresis saturation characteristic instead of a single-valued saturation curve. This parameter is enabled only if the Saturable core parameter is selected. Default is cleared.

Hysteresis Mat file

The Hysteresis Mat file parameter is enabled only if the Simulate hysteresis parameter is selected.

Specify a .mat file containing the data to be used for the hysteresis model. When you open the Hysteresis Design Tool of the Powergui, the default hysteresis loop and parameters saved in the hysteresis.mat file are displayed. Use the Load button of the Hysteresis Design tool to load another .mat file. Use the Save button of the Hysteresis Design tool to save your model in a new .mat file.

Measurements

Select Winding voltages to measure the voltage across the winding terminals of the Saturable Transformer block.

Select Winding currents to measure the current flowing through the windings of the Saturable Transformer block.

Select Flux and excitation current (Im + IRm) to measure the flux linkage, in volt seconds (V.s), and the total excitation current including iron losses modeled by Rm.

Select Flux and magnetization current (Im) to measure the flux linkage, in volt seconds (V.s), and the magnetization current, in amperes (A), not including iron losses modeled by Rm.

Select All measurement (V, I, Flux) to measure the winding voltages, currents, magnetization currents, and the flux linkage.

Default is None.

Place a Multimeter block in your model to display the selected measurements during the simulation.

In the Available Measurements list box of the Multimeter block, the measurements are identified by a label followed by the block name.

Measurement

Label

Winding voltages

U_LeftWinding_1:
U_TapWinding_2.1:
U_RightWinding_1:

Winding currents

I_LeftWinding_1:
I_TapWinding_2.1:
I_RightWinding_1:

Excitation current

Iexc:

Magnetization current

Imag:

Flux linkage

Flux:

Parameters Tab

Units

Specify the units used to enter the parameters of the Multi-Winding Transformer block. Select pu to use per unit. Select SI to use SI units. Changing the Units parameter from pu to SI, or from SI to pu, will automatically convert the parameters displayed in the mask of the block. The per unit conversion is based on the transformer rated power Pn in VA, nominal frequency fn in Hz, and nominal voltage Vn, in Vrms, of the windings. Default is pu.

Nominal power and frequency

The nominal power rating, in volt-amperes (VA), and nominal frequency, in hertz (Hz), of the transformer. Note that the nominal parameters have no impact on the transformer model when the Units parameter is set to SI. Default is [75e3 60].

Winding nominal voltages

Specify a vector containing the nominal RMS voltages, in Vrms, of the windings on the left side, followed by the nominal RMS voltages of the windings on the right side. You don't have to specify the individual tap nominal voltages. Default is [ 14400 120 120 120 ].

Winding resistances

Specify a vector containing the resistance values of the windings on the left side, followed by the resistance values of the windings on the right side. You don't have to specify the individual tap resistances. Default is [ 0.005 0.005 0.005 0.005] when the Units parameter is pu and [13.824 0.00096 0.00096 0.00096] when the Units parameter is SI.

Winding leakage inductances

Specify a vector containing the leakage inductance values of the windings on the left side, followed by the leakage inductance values of windings on the right side. You don't have to specify the individual tap leakage inductances. Default is [ 0.02 0.02 0.02 0.02 ] when the Units parameter is pu and [0.14668 1.0186e-05 1.0186e-05 1.0186e-05] when the Units parameter is SI.

Magnetization resistance Rm

The magnetization resistance Rm, in ohms or in pu. Default is 50 when the Units parameter is pu and 1.3824e+05 when the Units parameter is SI.

Magnetization inductance Lm

The Magnetization inductance Lm parameter is not accessible if the Saturable core parameter on the Configuration tab is selected.

The magnetization inductance Lm, in Henry or in pu, for a nonsaturable core. Default is 50 when the Units parameter is pu and 366.69 when the Units parameter is SI.

Saturation characteristic

This parameter is accessible only if the Saturation core parameter on the Configuration tab is selected.

The saturation characteristic for the saturable core. Specify a series of current/ flux pairs (in pu) starting with the pair (0,0). Default is [ 0,0 ; 0.0024,1.2 ; 1.0,1.52 ] when the Units parameter is pu and [0 0;0.017678 64.823;7.3657 82.109] when the Units parameter is SI.

Advanced Tab

Break Algebraic loop in discrete saturation model

When you use the block in a discrete system, you will get an algebraic loop. This algebraic loop, which is required in most cases to get an accurate solution, tends to slow down the simulation. However, to speed up the simulation, in some circumstances, you can disable the algebraic loop by selecting Break Algebraic loop in discrete saturation model. You should be aware that disabling the algebraic loop introduces a one-simulation-step time delay in the model. This can cause numerical oscillations if the sample time is too large. Default is cleared.

Examples

The power_OLTCregtransformer example uses three Multi-Winding Transformer blocks to implement a three-phase On Load Tap Changer (OLTC) transformer.

Introduced before R2006a

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