To expand on that a little, an AC induction motor spins because there are rotating magnetic fields in the stator (stationary part) and they induce current to flow in the rotor (rotating part), which creates magnetic fields there at the same time. These opposing magnetic fields repel each other making the rotor spin. If you apply DC to one set of windings in the stator, the magnetic field that creates in the stator is no longer rotating. The induced magnetic field in the rotor then tries to align itself with it, binging it to a stop (the zero Hz Lionel is referring to).
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