Constant Current Load (Three-Phase)

Three-phase constant current load

Since R2021a

• 

Libraries:
Simscape / Electrical / Passive

Description

The Constant Current Load (Three-Phase) block implements a constant current load for a three-phase supply.

This block consumes a current equal to the value of the Consumed current (RMS) parameter as long as the voltage from the three-phase supply is equal to or greater than the value specified for the Minimum supply voltage (phase-to-phase RMS) parameter.

When the voltage from the three-phase supply drops below the value of Minimum supply voltage (phase-to-phase RMS), the load behaviour changes and the block models a load with constant resistance.

Equations

If the three-phase voltages are balanced, the phase-to-phase RMS voltage is defined by this equation:

$$V_{lin{e}_{RMS}}=\sqrt{{\left(v_a-v_{dc}\right)}^2+{\left(v_b-v_{dc}\right)}^2+{\left(v_c-v_{dc}\right)}^2},$$

where $$v_{dc}=\frac{v_a+v_b+v_c}{3}.$$

The currents for each of the three phases are defined by this equation:

$$i_k(t)=\frac{v_k(t)}{R_{equiv}},$$

where R_equiv is the equivalent resistance and depends on value of the Minimum supply voltage (phase-to-phase RMS) parameter.

If the voltage from the three-phase supply is greater than the value specified for the Minimum supply voltage (phase-to-phase RMS) parameter, the equivalent resistance is defined by:

$$R_{equiv}=\frac{\frac{v_{pk}}{\sqrt{2}}}{I_{RM{S}_{consumed}}},$$

where v_pk is the voltage peak magnitude and I_RMSconsumed is the value of the Consumed current (RMS) parameter.

If the voltage from the three-phase supply is less than the value specified for the Minimum supply voltage (phase-to-phase RMS) parameter, the equivalent resistance is defined by:

$$R_{equiv}=\frac{v_{phRM{S}_{min}}}{I_{RM{S}_{consumed}}},$$

where $$v_{phRM{S}_{min}}=\frac{v_{lineRM{S}_{min}}}{\sqrt{3}}$$ is the phase-to-ground RMS minimum voltage.

Faults

The Constant Current Load (Three-Phase) block allows you to model an electrical fault as an open circuit. The block can trigger fault events either:

• At a specific time

• When a power limit is exceeded for longer than a specific time interval

You can also choose whether to issue an assertion when a fault occurs by using the Reporting when a fault occurs parameter. The assertion can take the form of a warning or an error. By default, the block does not issue an assertion.

Load-Flow Analysis

If the block is in a network that is compatible with frequency-time simulation mode, you can perform a load-flow analysis on the network. A load-flow analysis provides steady-state values that you can use to initialize a machine.

For more information, see Perform a Load-Flow Analysis Using Simscape Electrical and Frequency and Time Simulation Mode.

Ports

Conserving

~ — Three-phase voltage

electrical

Expandable three-phase electrical port associated with the three-phase voltage.

Parameters

Modeling option — Whether to model composite or expanded three-phase ports

Composite three-phase ports (default) | Expanded three-phase ports

Whether to model composite or expanded three-phase ports.

Composite three-phase ports represent three individual electrical conserving ports with a single block port. You can use composite three-phase ports to build models that correspond to single-line diagrams of three-phase electrical systems.

Expanded three-phase ports represent the individual phases of a three-phase system using three separate electrical conserving ports.

Main

Consumed current (RMS) — Root mean square consumed current

1 A (default) | scalar

Root mean square current consumed by the block.

Minimum supply voltage (phase-to-phase RMS) — Minimum supply voltage

10 V (default) | scalar

Minimum voltage, in phase-to-phase RMS, that the supply must provide for the block to act as a current load.

Faults

Enable open-circuit fault — Whether to enable faults modeling

Off (default) | On

Select On to enable faults modeling and expose parameters that allow you to select the reporting method and specify the trigger mechanism.

Open-circuit conductance — Open-circuit conductance

1e-4 S (default) | scalar

Conductance during the open-circuit state.

Dependencies

To enable this parameter, set Enable open-circuit fault to On.

Reporting when a fault occurs — Whether to issue an assertion when a fault occurs

None (default) | Warn | Error

Choose whether to issue an assertion when a fault occurs:

• None — The block does not issue an assertion.

• Warn — The block issues a warning.

• Error — Simulation stops with an error.

Dependencies

To enable this parameter, set Enable open-circuit fault to On.

Fault trigger — Trigger mechanism

Temporal (default) | Behavioral

Whether to trigger the fault based on temporal or behavioral conditions.

Dependencies

To enable this parameter, set Enable open-circuit fault to On.

Simulation time for fault event — Time before entering faulted state

1 s (default) | scalar

Simulation time when the block enters the faulted state.

Dependencies

To enable this parameter, set Enable open-circuit fault to On and Fault trigger to Temporal.

Maximum permissible power — Power threshold to fault transition

inf W (default)

Maximum permissible power value. If the power exceeds this value for longer than the Time to fail when exceeding power parameter value, then the block enters the faulted state.

Dependencies

To enable this parameter, set Enable open-circuit fault to On and Fault trigger to Behavioral.

Time to fail when exceeding power — Maximum length of time the power exceeds the threshold

1 s (default)

Maximum length of time that the power can exceed the maximum permissible value without triggering the fault.

Dependencies

To enable this parameter, set Enable open-circuit fault to On and Fault trigger to Behavioral.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2021a