Four-quadrant DC magnet power supply with fast dynamic response and low ripple content

Conventional DC magnet power supplies are composed of transistor banks operating in the active region, connected in series with a pre-regulated DC voltage obtained from a phase-controller rectifier. However, this configuration is very inefficient and large in volume because of the power dissipation across the transistor bank. To alleviate these problems, a power supply configuration based on a combination of a frequency converter and a dual converter is proposed here. The dual converter is used with circulating current mode for smooth transition of output current polarity. The frequency converter is used at the front end of the dual converter to boost the AC line frequency and improve the dynamic response without increasing the ripple content. The closed loop control of the dual converter in the proposed power supply configuration is designed to provide the required regulation and dynamic response. Analytical results are verified by experimental results using a 400 Hz frequency converter