Losses in superconducting coils of 1kWh/1MW SMES

The in-situ measurements of pulse losses are carried out for the total syst em of ESK (Experimental SMES(Superconducting Magnetic Energy Storage) of Ky ushu Electric Power Co.) with the capacity of 1kWh/1MW which has been compl eted in 1998. ESK has six toroidal coils wound by Rutherford cables, each c oil being contained in a fiber reinforced plastic (FRP) vessel set up in a Dewar. The loss was calculated by the method to measuring the decrement of liquid helium (LHe) level in each vessel. The form of current variation for the measurement is a repeated triangular wave form. The charge-discharge r ate was changed from 10A/s to 140A/s. Although there are considerable error s in the measurements, agreement between the measured results and theoretic al calculations is satisfactory in view of the limited conditions of the in -situ measurement for the SMES coils of this scale. The origins of the loss are discussed in detail.