This can happen when you have an algebraic loop in Simulink. This happens when a block's output depends directly on its input, so Simulink cannot solve it step-by-step and has to iterate to solve. Sometimes this iterative solution can fail, which is what you're seeing.
In the context of Simscape, this happens when you are measuring a Simscape output, doing a direct calculation on it, and applying this value back as an input to Simscape.
If your algorithm is discretely sampled, you should add a Unit Delay before that measured "Stator Current" is fed to the controller -- this can represent a sensor delay. If it's a continuous algorithm, you can similarly break the algebraic loop by using a low-pass filter (Transfer Fcn block).
- Sebastian
