Lenz's law states that eddy currents are created as the magnetic field passs through a conductive material. As a magnet passes across a closed circuit coil (an inductor), current is induced. The induced current creates a magnetic field opposing the magnet. At slow velocities the current is in phase with the magnet creating drag forces. This is illustrated in figure 1. High velocities cause the induced current to lag, or be delayed, creating levitation forces. The high velocity is illustrated in figure 2.

Figure 1 - Slow Moving Magnet Across Coil

Figure 2 - Fast Moving Magnet Across Coil