Description
The model has the comment "Use this model if the pump characteristics is of secondary interest."
However, even if the values for the pump characteristic as default has zero impact on the rest of the model (as far as I can see) incorrect values will still lead to a failed simulation.
This is slightly complicated - but as far as I can see:
For the default case N will be determined from head, and eta a fixed value so that power consumption does in fact not depend on the speed.
The equation for N is complicated, but even for a linear flow characteristic it is a quadratic equation that cannot be solved for all values of head (seems it is a minimum allowed value).
Values below the minimum may be non-physical - but a proper warning/error is preferable to having a non-linear system that cannot be solved.
Assuming this is correct I would propose to introduce a simpler variant of ControlledPump (either as parameter or as a separate model) without 'N'; possibly with monitoring for this issue.
To clarify: the simpler variant will simulate in more cases than the current one; and produce the same results when both work - and can be made by "just disabling N and its equations".