A new RMF stirrer using AISI4140 mild steel: Energy optimization application

Abstract

This study examines the development of a novel FPGA-based RMF stirrer system. The system has been designed as a 3-phase system, with each phase being fed by PWM voltage with a phase difference of 120 degrees. In case the system is driven at a 100 % duty cycle, the force acting on the magnetic fish remains continuous and constant until the subsequent phase changes. In such a case, at speeds under 400 rpm, the speed of the magnetic fish fails to be synchronized with the phase change speed. The magnetic fish, therefore, rotates more than 120 degrees and the force is observed to cause a braking effect. Both fluid logic control (FLC) and virtual model control (VMC) were utilised to enable the system to be driven at a different duty cycle. The energy efficiency of the system for fluids with different viscosities has been attempted to be thereby improved with a lower current and shorter excitation time. With FLC and VMC control, the energy consumed by the system is reduced and the efficiency is increased, and approximately 95 % energy gain is obtained for liquids with viscosity up to 1.03 Pas. It has been experimentally proven that a lower limit value of the duty cycle of the PWM signal applied to the drive circuit of the system depends on the viscosity of the mixed liquid and a lower limit value increases with increasing viscosity. It has also been found that controlling the system with FLC and VMC does not have a great effect on the energy gain.