Abstract: In a magnetic floating type of super high speed transportation system using a linear synchronous motor system as its drive system in which a field magnet is carried on a train and a series of armature coils are provided along a track, a speed of a train is regulated under control of a frequency converter of the variable frequency and voltage type for supplying power to the armature coils. For the speed regulation, a relative position of the field magnet to the armature coils is detected to form a train of position detecting pulses. A reference frequency pattern with a frequency corresponding to a speed command is formed. A phase difference between the reference frequency pattern and the position detecting pulse train is detected. A propulsion force command of a linear motor is obtained by setting different limit values in the positive and negative parts of the phase difference signal. A sinusoidal current waveform pattern is formed in synchronism with the position detecting pulse train.