Force mismatch in Magnetostatic and Transient SImulation

For an IPM motor, I want to look at the forces on the rotor while it is running. But magnetostatic and transient simulations are giving me different results? I am using Electronic desktop 2019.

Left side pictures are transient simulation and right side are magnetostatic. The mesh settings for both simulations are same. Torque matches nicely, but force is not making any sense.


  • nchodenchode Forum Coordinator


    What is your excitation setup for winding in both cases? are you providing any excitation to the windings in both cases or are you just checking the cogging torque in un excited state?

    Results will be same only in the winding unexcited state.

    If you are exciting the windings in transient simulation, torque in both the cases will not be same as magnetostatics simulation is a DC-magnetic simulation

    Observation from torque graph you shared - for a transient simulation the torque graph should ramp up from zero to steady state. But what you shared is starting from some initial value at 0 time.



  • KKBHKKBH Member

    I am injecting some Iq current with Id=0 in both cases. That's why there is an average torque and cogging torque can be seen on top of that.

    Both simulations have same equivalent excitation (current depending on rotor position), that's why the torque produced is same.

    The problem is I am not sure whether applying Iq current to the motor will produce force on the rotor. Since both simulations are giving different results.


  • nchodenchode Forum Coordinator


    Whether it is transient or static simulation the resultant torque could be approximately same. This is because torque is angular twist acting, due to the whole airgap magnetic field, on the rotor at any instance.

    But when it comes to force what you are looking is at a particular position along the x or y axis .

    Here there is a difference between transient and static simulation

    In transient simulation you have a motion setup and position of the rotor is changing with respect to time and force along the axis is captured continuously with time varying fields.

    Where as in static simulation the rotor is static at a particular position at each step and it will not take continuous variation with time in to account(static simulation can't take time varying field in to account). So, it will be different.

    If you think there is some misinterpretation of what you are simulating, please consider sharing some screen shots that will explain your excitation and motion setup for both simulations explaining how you defined  Iq current with Id=0 in both cases as clear as possible.

    Note: Ansys employees can't access any attachments (pictures/documents/simulation files) shared in the learning forum. Kindly use upload image option while inserting any images.



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