Energy transfer experiments between 3 MJ and 4 MJ pulsed superconducting magnets

The pulsed power supply system for a 3 MJ pulsed superconducting magnets by using an energy storage magnet and a transfer circuit was constructed. It is composed of both 3 MJ and 4 MJ pulsed superconducting magnets (named PSM-3 and SMES-4, respectively) and the energy transfer apparatus which consists of the chopper circuit with a capacity of about 5000 kW. The reversible energy transfer experiments between SMES-4 and PSM-3 were carried out, and with the SMES-4 charged up to 4.24 MJ initial energy, the PSM-3 was successfully charged up to 2.45 MJ (4950 A, Bm: 5.94 T) in 1.5 seconds and also up to 2.9 MJ (5400 A, Bm: 6.48 T) in 3.0 seconds. The maximum delivery power was about 3270 kW. The energy transfer efficiency in one way transfer was about 93 %, and the current ripple was less than 0.01% of a rating current. The two pulsed magnets showed very stable performances during the energy transfers.