ENN Science and Technology Development Co., Ltd. (ENN Fusion Technology R&D Center) is upgrading its compact fusion research facility EXL-50 to EXL-50U. Both devices are the conventional conductor tokamak, on which the magnet power supply system is composed by 1 TF (Toroidal Field) power supply, 1 CS (Center Solenoid) power supply and 10 PF (Poloidal Field) power supplies PF1-10. All 12 sets of power supply system are powered by 2 AC pulse generators and output DC current through thyristor-based converters.

This study aims to design EXL-50U magnet power supply for satisfying high parameter requirements of EXL-50U.

Power supply capacity was the first concern for upgrading and the corresponding protection strategies under high parameter conditions was taken into account as well. The configuration of AC pulse generator was introduced at the beginning. Then transformers and converters were listed and designed in scheme. Control system and protection process were implemented respectively, followed by detail power supply system illustration and commissioning waveforms display for each power supply.

The reliability and controllability of developed power supply system are verified by the waveforms that forms plasma current under the condition of CS breakdown.

It is proved that this power supply system can work stably, and output waveforms can be repeated no matter it works alone or under complex condition of joint debugging.