The Choice of the Rotor Geometry of Synchronous Reluctance Machines for Electric Drives for Cold-Rolling Tube Mills

Cold rolling mills, like most metallurgical electrically driven installations, are characterized by low-speed operating modes that involve shock loads. The use of synchronous reluctance machines integrated into controlled electric drives enhances the productivity of the mill, the quality of products, and the energy performance due to their good controllability, overload capacity, having no losses in the rotor, and low inertia of the latter. The choice of the rotor geometry significantly affects the characteristics of the electric drive, since the conversion of electromechanical energy in synchronous reluctance machines is possible only owing to the rotor’s magnetic nonsymmetry. The validation of the rotor geometry is based on comparison of the performance criteria of several options. These criteria include the specific and overload electromagnetic torques, power factor, and dynamic capabilities. It has been established that an increase in the number of live wires results in enhanced performance of the electric drive of the mill due to the increased voltage margin but requires extra expenditure on electric converters. An explicitly salient pole (SP) rotor, a circular rotor with a transverse lamination (TLA), an explicitly salient pole rotor with a transverse lamination (SP–TLA) and an axially laminated (ALA) rotor are compared. It is shown that a round rotor with a transverse lamination (TLA) can be recommended for the electric feed of the cold rolling mill. It provides a balanced solution according to power and energy criteria with good control capabilities and sufficient mechanical strength.