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Delta-Connected Load

Three-phase load wired in delta configuration

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Passive Devices

Description

The Delta-Connected Load block models a three-phase load wired in a delta configuration. Each limb of the load can include any combination of a resistor (R), capacitor (C), and inductor (L), connected in series or in parallel.

You can specify values for the R, L, and C components directly in terms of resistance, inductance, and capacitance, or by rated powers at a rated voltage and frequency.

  • If you parameterize the block directly in terms or R, L, and C values, then for initialization provide a three-element row vector of initial voltages for a capacitor, and a three-element row vector of initial currents for an inductor.

  • If you parameterize the block in terms of rated powers, then specify initial conditions in terms of an initial voltage, initial voltage phase, and initial frequency. For example, if the load is connected directly to a three-phase voltage source, then the initial conditions are identical to the source values for RMS line voltage, frequency, and phase shift. To specify zero initial voltage magnitude, set the initial voltage to 0.

For certain combinations of R, L, and C, for some circuit topologies, specify parasitic resistance or conductance values that help the simulation to converge numerically. These parasitic terms ensure that an inductor has a small parallel resistive path and that a capacitor has a small series resistance. When you parameterize the block in terms of rated powers, the rated power values do not account for these small parasitic terms. The rated powers represent only the R, L, and C values of the load itself.

Parameters

Main Tab

Parameterization

Select one of these values:

  • Specify by rated power — Specify values for the R, L, and C components by rated powers at a rated voltage and frequency. This is the default.

  • Specify component values directly — Specify values for the R, L, and C components directly in terms of resistance, inductance, and capacitance.

Switching the Parameterization value resets the Component structure value. Select the component parameterization option first, and then the component structure. If you later switch the Parameterization value, check the Component structure value and reselect it, if necessary.

Component structure

Select the desired combination of a resistor (R), capacitor (C), and inductor (L), connected in series or in parallel. The default is R, resistor.

Rated voltage

Voltage for which load powers are specified. This parameter is visible only when you specify values by rated power. The default value is 2.4e4 V.

Real power

Total real power dissipated by three-phase load when supplied at the rated voltage. This parameter is visible only when you specify values by rated power and select a component structure that includes a resistor. The value must be greater than 0. The default value is 1000 W.

Rated electrical frequency

Frequency for which reactive load powers are specified. This parameter is visible only when you specify values by rated power. The default value is 60 Hz.

Inductive reactive power

Total inductive reactive power taken by the three-phase load when supplied at the rated voltage. This parameter is visible only when you specify values by rated power and select a component structure that includes an inductor. The value must be greater than 0. The default value is 100 V*A.

Capacitive reactive power

Total capacitive reactive power taken by the three-phase load when supplied at the rated voltage. This parameter is visible only when you specify values by rated power and select a component structure that includes a capacitor. The value must be less than 0. The default value is -100 V*A.

Resistance

The resistance of each of the load limbs. This parameter is visible only when you specify component values directly and select a component structure that includes a resistor. The default value is 1 Ohm.

Inductance

Inductance of each of the load limbs. This parameter is visible only when you specify component values directly and select a component structure that includes an inductor. The default value is 0.001 H.

Capacitance

Capacitance in each of the load limbs. This parameter is visible only when you specify component values directly and select a component structure that includes a capacitor. The default value is 1e-6 F.

Parasitics Tab

Parasitic series resistance

Represents small parasitic effects. The parameter value corresponds to the series resistance value added to all instances of capacitors in the load. The default value is 1e-6 Ohm.

Parasitic parallel conductance

Represents small parasitic effects. The parameter value corresponds to the parallel conductance value added across all instances of inductors in the load. The default value is 1e-6 1/Ohm.

Initial Conditions Tab

Terminal voltage magnitude

Expected initial RMS line voltage at the load. This parameter is visible only when you specify values by rated power. The default value is 2.4e4 V.

Terminal voltage angle

Expected initial phase of the voltage at the load. This parameter is visible only when you specify values by rated power. The default value is 0 deg.

Frequency

Expected initial frequency at the load. This parameter is visible only when you specify values by rated power. The default value is 60 Hz.

Initial inductor current [ Ia Ib Ic ]

Initial current in the a, b, and c phase inductors, respectively. This parameter is visible only when you specify component values directly and select a component structure that includes an inductor. The default value is [0 0 0] A.

Initial capacitor voltage [ Va Vb Vc ]

Initial voltage across the a, b, and c phase capacitors, respectively. This parameter is visible only when you specify component values directly and select a component structure that includes a capacitor. The default value is [0 0 0] V.

 Block Parameterization

Ports

The block has one expandable three-phase port, ~.

Introduced in R2013b

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