METHOD AND APPARATUS FOR DECELERATING A MACHINE REEL OF AN UNWINDER

A method and apparatus are provided for decelerating an inverter-controlled machine reel in a paper machine. The method includes detecting a break in a paper web from a machine reel, determining the inertia of the machine reel, determining continuously the angular speed of the machine reel, and determining continuously the torque required to decelerate the machine reel, on the basis of the determined inertia and angular speed, for the purpose of stopping the machine reel in a predefined time. The method also includes decelerating the machine reel electrically to stop the machine reel, in accordance with the determined torque, and using a mechanical brake when the rotation speed of the machine reel is lower than a predefined rotation speed and when the torque obtained by electrical deceleration is too small to stop the machine reel in a predefined time.