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Zigzag-Delta11-Wye Transformer

Linear nonideal zigzag-delta11-wye transformer with three-limb core

Library

Passive Devices / Transformers

Description

The Zigzag-Delta11-Wye Transformer block models a linear, nonideal transformer with a three-limb core, in which the primary windings are configured in a zigzag connection and there are delta secondary windings and wye secondary windings. You can specify the phase offset between the zigzag and wye windings via a block parameter. The delta voltages lead the wye voltages by 30 degrees, hence the name 11 o’clock delta. The block includes linear winding leakage and linear core magnetization effects.

The figure shows the equivalent circuit diagram for the zigzag-delta11-wye transformer.

  • w1zz1 is the primary winding located on the first limb of the core, connected between the a-phase and the negative terminal of winding w1zz5.

  • w1zz2 is the primary winding located on the second limb of the core, connected between the b-phase and the negative terminal of winding w1zz6.

  • w1zz3 is the primary winding located on the third limb of the core, connected between the c-phase and the negative terminal of winding w1zz4.

  • w1zz4 is the primary winding located on the first limb of the core, connected between the zigzag neutral point and the negative terminal of winding w1zz3.

  • w1zz5 is the primary winding located on the second limb of the core, connected between the zigzag neutral point and the negative terminal of winding w1zz1.

  • w1zz6 is the primary winding located on the third limb of the core, connected between the zigzag neutral point and the negative terminal of winding w1zz2.

  • w2a is the secondary winding connected between the a-phase and the c-phase.

  • w2b is the secondary winding connected between the b-phase and the a-phase.

  • w2c is the secondary winding connected between the c-phase and the b-phase.

  • w3a is the secondary winding connected between the a-phase and the secondary neutral point.

  • w3b is the secondary winding connected between the b-phase and the secondary neutral point.

  • w3c is the secondary winding connected between the c-phase and the secondary neutral point.

Display Options

You can display the transformer per-unit base values in the MATLAB® command window using the block context menu. To display the values, right-click the block and select Power Systems > Display Base Values.

Parameters

Main Tab

Rated apparent power

Apparent power flowing through the transformer when operating at rated capacity. The default value is 100e6 V*A.

Primary rated voltage

RMS line voltage applied to the primary winding under normal operating conditions. The default value is 24e3 V.

Delta secondary rated voltage

RMS line voltage applied to the delta secondary winding under normal operating conditions. The default value is 4160 V.

Wye secondary rated voltage

RMS line voltage applied to the wye secondary winding under normal operating conditions. The default value is 4160 V.

Rated electrical frequency

Rated or nominal frequency of the AC network to which the transformer is connected. The default value is 60 Hz.

Wye secondary phase shift

The phase offset between the zigzag and wye secondary windings. The default value is -7.5 deg.

Impedances Tab

Parameters in this tab are expressed in per-unit (pu). For more information, see Per-Unit System of Units.

Primary leakage resistance (pu)

Power loss in the primary winding. The default value is 0.01.

Primary leakage reactance (pu)

Magnetic flux loss in the primary winding. The default value is 0.001.

Delta secondary leakage resistance (pu)

Power loss in the delta secondary winding. The default value is 0.01.

Delta secondary leakage reactance (pu)

Magnetic flux loss in the delta secondary winding. The default value is 0.001.

Wye secondary leakage resistance (pu)

Power loss in the wye secondary winding. The default value is 0.01.

Wye secondary leakage reactance (pu)

Magnetic flux loss in the wye secondary winding. The default value is 0.001.

Shunt magnetizing resistance (pu)

Magnetic losses in transformer core. The default value is 500.

Shunt magnetizing reactance (pu)

Magnetic effects of the transformer core when operating in its linear region. The default value is 500.

Initial Conditions Tab

Initial primary currents

Current through the primary leakage inductors at time zero. The default value is [0, 0, 0] A.

Initial delta secondary currents

Current through the delta secondary leakage inductors at time zero. The default value is [0, 0, 0] A.

Initial wye secondary currents

Current through the wye secondary leakage inductors at time zero. The default value is [0, 0, 0] A.

Initial fluxes

Magnetic fluxes in the limbs of the core at time zero. The default value is [0, 0, 0] Wb.

Ports

The block has the following ports:

~1

Expandable three-phase port for primary winding

~2

Expandable three-phase port for delta secondary winding

~3

Expandable three-phase port for wye secondary winding

n3

Electrical conserving port associated with the wye secondary winding neutral point

Introduced in R2015a

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