Magnetomotive device based on reluctance force

Magnetic Elements

The Reluctance Force Actuator block models a generic magnetomotive device based on reluctance force.

The block is based on the following equations:

$$F=-0.5\cdot {\Phi}^{2}\cdot \frac{d\Re}{dx}$$

$$\Re (x)=\frac{x}{{\mu}_{0}\cdot {\mu}_{r}\cdot A}$$

$$u=dx$$

where

F | Reluctance force |

Φ | Flux in the magnetic circuit |

$$\Re $$ | Reluctance |

x | Thickness or length of the air gap |

μ_{0} | Permeability constant |

μ_{r} | Relative permeability of the material |

A | Cross-sectional area of the section being modeled |

u | Velocity |

Connections N and S are magnetic conserving ports, and connections C and R are mechanical translational conserving ports. The magnetic force produced by the actuator acts to close the gap, therefore the resulting force is negative when it acts from C to R.

Use the **Variables** tab in the block dialog
box (or the **Variables** section in the block Property
Inspector) to set the priority and initial target values for the block
variables prior to simulation. For more information, see Set Priority and Initial Target for Block Variables.

The current excitation in the system is constant.

Only axial reluctance is modeled.

**Initial air gap**Thickness or length of air gap at the beginning of simulation. The default value is

`2`

mm.**Minimum air gap**Minimal value of air gap, with the reluctance force acting to close the air gap. The parameter value has to be greater than 0. The default value is

`1e-4`

mm.**Cross-sectional area**Area of the section being modeled. The default value is

`0.01`

m^2.**Relative permeability of material**Relative permeability of the section material. The default value is

`1`

.**Contact stiffness**Stiffness that models the hard stop at the minimum air gap position. The default value is

`10e6`

N/m.**Contact damping**Damping that models the hard stop at the minimum air gap position. The default value is 500 N/(m/s).

The block has the following ports:

`N`

Magnetic conserving port associated with the block North terminal.

`S`

Magnetic conserving port associated with the block South terminal.

`R`

Mechanical translational conserving port associated with the rod.

`C`

Mechanical translational conserving port associated with the case.

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