Experimental investigation for power loss measurement of superconducting coils under harmonic supply current

•AC loss of HTS coil under nonsinusoidal current.•Comparison with sinusoidal shows higher AC losses in the same peak current for nonsinusoidal current.•The investigation on loading factor and some discussions on quench.•Proper to use for superconducting machine design. Nowadays in the competitive generation and consumption electrical network, the efficiency is the key elements which should be carefully considered before purchasing electrical machines. It is not only important for achieving a better performance but also to keep the total ownership cost of the machine as low as possible. For this purpose, many research efforts have been done to involve superconducting material in electrical machine fabrication process. Recently, with continuous fast-development in production technology of second generation high temperature superconducting tapes, it is likely to achieve a very high efficiency with superconducting electrical machines. In order to investigate the efficiency, one needs to measure the losses of the superconducting wires under different operating conditions. It is quite common for an electrical machine to work under distorted supply current because they normally are driven with non-sinusoidal current of speed drives or supplying non-linear loads. In this paper, power loss of a double pancake high temperature superconducting coil which is supplied by harmonic-wave current has been experimentally measured and then, the results discussed which have shown, the power losses of distorted currents are wave-shape dependent and this loss decreases the loading ratio i.e. the ratio of operation current respect to critical current, significantly.