Development of a 1.2-MVA self-commutated power supply for a magnet test system

This paper presents the design and development of a self-commutated power supply rated at 1.2 MVA intended for excitation of ground coils inducing forces in a large-scaled magnet. In order to create the required magnetic forces, the developed power supply delivers current to the ground coils at different amplitudes, frequencies and phases. The objective of this test system is to study vibrations in the magnets, therefore an accurate current control is required. The current reference is composed of several frequencies superimposed, varying according system requirements, thus a synchronous reference frame controller is inapplicable. On the other hand, mutual inductance induced between ground coils perturbs the current control system transferring small amounts of active power between the ground coils. This paper focuses on the control and configuration of the power supply. Current control and mutual inductance effects are reported, covering design considerations, simulations, and field tests results. These test results prove satisfactory performance of this power supply for large-scaled magnet applications.