PURPOSE: To provide the subject device having a specific braking circuit and capable of generating a sufficient braking action to certainly prevent troubles caused by the rotation of spindles generated by doffing.

CONSTITUTION: A coil S is connected to a coil T to be parallel when a switch 6, which connects a circuit including two coils R and T of a polyphase synchronous motor, is closed, then, a switch 7 is closed after a little while. The intensity of magnetic fluxes is increased by adding a magnetic flux generated by the coil S, the direction of the magnetic fluxes is changed and the magnetic fluxes are shifted to about 30° in the opposite direction to the direction of rotation of a spindle winding the coil yarn on a bobbin. By the rapid change of the magnetic fluxes in the direction of opposite rotation, a torque is generated on the rotor of the polyphase synchronous motor acting in this direction. When a dc voltage is set to a suitable value, the spindle is stopping during doffing or at least moves in an angle causing no troubles.