# Linear Joints

### Actuator, Pump, Relay

For the analysis of any linear motion as you may need for actuators, pumps or relais you can use the linear joint type. As with the revolute joint it is possible to include friction or the mechanical magnetical coupling.

By using the 2D or 3D magnetodynamic time solution type you can define currents or voltages as tabular or mathematical functions of time. The results are magnetic fieldstrenght and fluxdensity as well as eddy currents, power losses, velocity and step size.

Next picture/movie shows fluxdensity result from a 2D relay simulation. On the right coil we switch on current. A magnetic field develops time dependent as well as force on the plunger. The force pushes the plunger to the right. At 15 mm displacement the plunger hits a wall and stops. Click on it to see a movie.

*Picture: Motion of Plunger (click to animate)*

Again the power losses because of this movement are analyzed. See the following picture/movie.

*Picture: Eddy Current on moving Relay*

The resulting losses are shown in a graph. Notice the peak at the position of the stop of the plunger.

*Picture: Resulting Losses*