Power Supplies

The power supply system consists of the power supplies for the superconducting and control coils, the beam and EC heating and current drive systems, and power supplies for auxiliary plant. Existing equipment is re-used where possible, on a rearranged AC supply network.

New power supply systems will be designed and manufactured to feed the superconducting TF, and PF coils. Typical operation of the TF coil power supply is that the TF coils are energized every day in the morning before the starting of the plasma experiments, and demagnetized after the experimental period. The PF coil power supply circuit components are a "Base PS", a "Booster PS", and a "Switching Network Unit (SNU) ".

In case a superconducting coil quenches or a power supply fails, a quench protection circuit is connected in series with the TF and PF coils to allow fast extraction of the coil energy. The quench-protection circuit consists of a DC current interrupter, discharge resistor, and pyro-breaker for back-up protection.

The in-vessel fast coils (copper) are powered by 4 quadrant thyristor converters. The sector coil power supply has 3 units, each one composed of a thyristor converter and an insulated gate bipolar triansistor (IGBT) inverter with 3-phases. Water-cooled aluminum bus-bars are planned for connecting the coils to the power supplies.

Among additional heating devices P-NBI, N-NBI, and ECRF, (41 MW for 100 s plasma heating), the P-NBI (60 MW power demand) and ECRF (30 MW power demand) will be connected to the 275 kV commercial power grid, together with the TF coil power supply. The conditions for power utilization from the commercial power grid is subject to negotiation with the electric power companies. The N-NBI (40MW power demand) and PF coil power supplies are connected to two existing motor generators (4 GJ, and 2.6 GJ).

An auxiliary power system serves clients throughout the plant, and interfaces to the off-site electricity supply network through the main power supply switchyard. It consists of an 80 MVA utility line, servicing load centres in the torus hall, power supply building, cryoplant building, and cooling plant.