PWM Control of a Magnetic Suspension System

Magnetic levitation of a metallic sphere motivates and inspires students to investigate and understand the fundamental principles of electrical engineering, such as magnetic design, circuit design, and control theory. This paper describes the operation of a pulsewidth modulation converter in a magnetic suspension system. The pulsewidth-modulated (PWM) converter illustrates modern principles of power electronics, such as PWM control, current-mode control, averaged and linearized models of switched-mode converters, and power supply design. The reduced size of the heat sink in the switched-mode converter compared with its linear amplifier counterpart clearly illustrates improved efficiency. The experimental system described levitates a 6-cm-diameter, 0.8-kg metallic sphere.