# Dynamic Load

**Libraries:**

Simscape /
Electrical /
Passive

## Description

The Dynamic Load block implements a dynamic load for a DC or AC supply.

If you set the **Load type** parameter to
`DC`

:

The consumed power of the block is equal to the

**P**port as long as it is greater than the value of the**Minimum consumed power**parameter and the voltage from the DC supply is equal to or greater than the value specified for the**Minimum supply voltage**parameter.When the voltage from the DC supply drops below the

**Minimum supply voltage**, the load behaviour changes and the block acts as a resistive load. If the supply voltage becomes negative, the block acts as an open circuit conductance.

To ensure smooth transitions between these behaviours, the block uses a third-order
polynomial spline with continuous derivatives. You can specify the width of this
transition using the **Transition voltage width** parameter.

If you set the **Load type** parameter to `AC`

,
this table shows how the block calculates the consumed active and reactive power based
on the voltage from the supply, *V*.

Range of V Values | Consumed Active and Reactive Power |
---|---|

$$V>{V}_{\mathrm{min}}$$ | $$\begin{array}{l}{P}_{actual}={P}_{in}\\ {Q}_{actual}={Q}_{in}\end{array}$$ |

$$V<{V}_{\mathrm{min}}$$ | The block models a load with an impedance equal to:$$\begin{array}{l}R={V}_{\mathrm{min}}^{2}\frac{{P}_{in}}{{P}_{in}^{2}+{Q}_{in}^{2}}\\ X={V}_{\mathrm{min}}^{2}\frac{{Q}_{in}}{{P}_{in}^{2}+{Q}_{in}^{2}}\\ Z=\sqrt{{R}^{2}+{X}^{2}}\end{array}$$ |

In these equations:

*V*is the value of the Minimum supply voltage (RMS) parameter._{min}*P*is the input active power of the Dynamic Load block, determined by external input port_{in}**P**.*P*is the consumed active power of the Dynamic Load block._{actual}*Q*is the input reactive power of the Dynamic Load block, determined by external input port_{in}**Q**.*Q*is the consumed reactive power of the Dynamic Load block._{actual}

The Dynamic Load block consumes or generates active
power depending on the polarity of input active power
*P _{in}*. If

*P*is greater than 0, the block consumes active power. If

_{in}*P*is less than 0, the block generates active power.

_{in}### Faults

To model a fault in the Dynamic Load block, in the
**Faults** section, click the **Add fault** hyperlink in
the parameter that corresponds to the specific fault that you want to model. When the
**Create Fault** window opens, you use it to specify the fault properties.
For more information about fault modeling, see Fault Behavior Modeling and Fault Triggering.

The Dynamic Load block allows you to model an electrical fault as an open circuit. The block can trigger fault events at a specific time.

### Load-Flow Analysis

If the block is in a network that is compatible with the 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

### Input

### Conserving

## Parameters

## Extended Capabilities

## Version History

**Introduced in R2020b**