Active Magnetic Bearing
Add an Active Magnetic Bearing node to model a radial magnetic bearing together with a PID controller. The controller determines the current in the coils of the bearing though a feedback mechanism by sensing the vibration levels at the bearing location. When added in Solid Rotor interface, the selection of the node corresponds to the cylindrical surface of the journal, whereas for a Beam Rotor, it is a point corresponding to the bearing location.
For a time-dependent analysis, the behavior of the bearing is nonlinear and control forces are nonlinear functions of both displacement and control current. In a stationary analysis, only a proportional controller is considered with a linearized force-displacement relation. In a frequency domain or eigenfrequency analysis, a linearized expression for the force as function of displacement and control current is considered. In this case also, a PID controller is used with control current now depending on both displacement and frequency. As a result, an active magnetic bearing in a frequency or eigenfrequency analysis works as an effective impedance that is a function of frequency. In this node, you specify the magnetic bearing parameters together with values for the controller gains.
Bearing Orientation
Use the settings in this section to define the local y direction of the bearing. Subsequent vector and matrix inputs are specified in the local directions specified here.
If the feature is added to a Solid Rotor, or Solid Rotor, Fixed Frame interface, enter the Bearing orientation vector defining the local x direction.
If the feature is added to a Beam Rotor interface, enter the Bearing orientation vector defining the local y direction. The direction given will be adjusted so that it is orthogonal to the rotor axis. The default value is the global y-axis.
You can further modify the orientation of local axis by entering an angle for the Rotation of the orientation vector around the bearing axis. The direction inferred from the previous setting will be rotated counterclockwise around the rotor axis.
Air Gap
Enter the Air gap, h, in the local lateral directions.
Control Parameters
Enter the values of the Proportional gain, Kp, Integral gain, Ki, Derivative gain, Kd, and Force constant, Fc, in the local lateral directions.
Currents
Bias currents in the magnetic bearings are used to support the static load of the rotor. If you use the same bias current in the positive and negative axes, the bearing will not support any static load. Enter the values of the bias currents in local directions for both positive and negative axes using the inputs Bias current, positive axis, ib,p and Bias current, negative axis, ib,n. The current in the coils is restricted not to go beyond a cutoff value for safety reasons. Enter the maximum allowed current in the coil in the Maximum current, imax, field.
Foundation Properties
Select one of the Fixed, Moving, Flexible, or Squeeze-film damper foundation options. If the model component also contains other structural physics interfaces such as Solid Mechanics, Multibody Dynamics, or Shell that have Attachment or Rigid Domain features, the above list is extended with the attachments and rigid domains available in these physics interfaces. In the Moving, Flexible, and Squeeze-film damper cases, the subnodes Moving Foundation, Flexible Foundation, or Squeeze-Film Damper are automatically added. If any of the attachments or rigid domains is selected, displacement and rotation of the selected feature are used as foundation motion. Attachments and rigid domains provide an easy way of coupling the rotor with the stator.
Location in User Interface
Context Menus
 Solid Rotor > Bearings > Active Magnetic Bearing
Solid Rotor, Fixed Frame > Bearings > Active Magnetic Bearing
Beam Rotor > Bearings > Active Magnetic Bearing
Ribbon
Physics tab with Solid Rotor or Solid Rotor, Fixed Frame selected:
Boundaries > Bearings > Active Magnetic Bearing
Physics tab with Beam Rotor selected:
Points > Bearings > Active Magnetic Bearing