The Rotating Domain node specifies which domains are rotating, relating the mechanical rotation α to the time periodic phase angle ϕTP. This node works in conjunction with the Rotational Continuity Pair node. The main input in this node is the Rotation angle during time periodic cycle αTP (SI unit: rad), which may be user defined or based on the Time periodic rotation and Rotation direction settings.

If Time periodic rotation is set to Synchronous (pole pair), the rotation angle is determined by the number of poles npoles as αTP = 4π/npoles. This is due to the fact that most of the fields in a synchronous machine are repeating after that angle.

If Time periodic rotation is set to Full mechanical revolution, the rotation angle becomes αTP = 2π if Rotation direction is set to Counterclockwise, or αTP = -2π if Rotation direction is set to Clockwise. This means that the specified regions rotate a complete turn in the specified direction during the time periodic frequency.

It is also possible to select Nonrotating, which results in αTP = 0. Finally, select User defined in order to manually enter a value of αTP. The default expression is if(mmtp.NoPoles==0,2*pi,4*pi/mmtp.NoPoles) which indicates a full rotation counterclockwise if the number of poles defined at the physics level is zero, or a pole pair synchronous counterclockwise rotation if the number of poles is set to a finite value. It is also possible to override this value, for example when simulating asynchronous machines.

Once αTP is defined, the mechanical rotation angle at a given frame is assumed to be proportional to the time periodic phase, as shown below.