Development of a Braking Device for a Step Drive of Vertical Displacement Actuators

Abstract

The conceptual design scheme of an electric drive for control rod vertical displacement consisting of an electromagnetically excited inductor motor and a variable-pole permanent magnet generator, both interconnected by a common shaft, is substantiated. For this design scheme, an approach to determining the common bore diameter for both machines is proposed, which takes into account the drive inertia moment and includes the outer diameter determination by using the known motor designing methods. The sequence of determining the following generator parameters is described: the number of rotor poles, the number of phase winding turns, the winding wire diameter depending on the required steady-state rotor rotation frequency, and the shaft torque versus the control rod weight. A separate generator for limiting the control rod insertion speed has been designed and manufactured. This generator is a two-phase six-pole machine with barium-ferrite permanent magnets on the rotor, and with a thick-walled partition installed in the stator bore and containing magnetically soft steel inserts located in places of abutment to stator teeth. Field studies of the developed generator were carried out. The obtained test results confirm the advisability of making a shift to using the two-machine electromechanical converter design of the step drive for nuclear reactor control rod vertical displacement owing to a wider range of possible steady-state speeds and an increased generator braking torque.