What is currently the limiting factor on the speed of maglev trains?

Question

What is currently the limiting factor on the speed of maglev trains?

Answer 1

In linear induction, wheels and drive trains are not present so there is no energy loss from rolling resistance or gearing.  Friction is not, therefore, a significant factor and this is the energy economy advantage in terms of mechanical efficiency that maglev has over a wheeled train.

The train's motion is still, however, limited by the power available to overcome its inertial mass and also air resistance which increases with the square of its speed - this applies to  maglev in the same way as it applies to a conventional train.