# Variable Inductor

Discrete variable inductor

• Library:
• Simscape / Electrical / Specialized Power Systems / Fundamental Blocks / Elements

• ## Description

The Variable Inductor block represents a linear time-varying inductor. It implements a discrete variable inductor as a current source. The impedance is specified by the Simulink input signal. The inductance value can be negative.

When you use a Variable Inductor block in your model, set the powergui block Simulation type to `Discrete`. The robust discrete solver is used to discretize the electrical model.

### Equations

The block uses the following equations for the relationship between the voltage, v, across the device and the current through the inductor, i. The block input specifies the value of the inductance. The flux linkage of the inductor is equal to the specified inductance multiplied by the inductor current:

`$v=\frac{d\left(phi\right)}{dt},$`

`$phi=L\ast i.$`

## Ports

### Input

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Input port associated with the inductance. The inductance can be negative and must be finite.

### Conserving

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Specialized electrical conserving port associated with the inductor positive voltage.

Specialized electrical conserving port associated with the inductor negative voltage.

## Parameters

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Robust integration method used by the block. The discrete solver method is automatically set to `Trapezoidal` when, in the powergui block, in the Preferences settings, you select Automatically handle discrete solver and Advanced tab solver settings of blocks.

The `Trapezoidal` robust solver is slightly more accurate than the `Backward Euler` robust solver, especially when the model is simulated at larger sample times. The `Trapezoidal` robust solver may produce slight damped numerical oscillations on machine voltage in no-load conditions, while the `Backward Euler` robust solver prevents oscillations and maintains good accuracy.

Lower limit on the absolute value of the signal at port L. This limit prevents the signal from reaching a value that has no physical meaning. The value of this parameter must be greater than 0.