Abstract: According to the present invention, a method of detecting water leakage in a coil, which determines whether or not cooling water leaks into an insulation layer, the water being supplied to a conductor of a coil covered with the insulation layer, including: applying an AC voltage to the conductor; bringing a surface electrode device into pressure contact with the insulation layer; grounding the surface electrode device through an impedance; measuring a potential of the surface electrode device; and determining that the cooling water leaks from the conductor into the insulation layer when a measured potential is higher than a potential of a normal coil

Abstract: An apparatus includes a vessel 10 for storing a liquid mixture 11 containing a liquid fuel 2 and an incompatible liquid 4 such as water or for allowing the liquid mixture 11 to flow therethrough, a vibrator 13 having at least one portion making contact with the liquid mixture in the vessel, a vibration generator 20 for vibrating the vibrator at high frequency, and a reflector 14 spaced from the vibrator 13 at a small distance. The incompatible liquid 4 is dispersed in and mixed with the fuel 2 by vibrating the vibrator at high frequency, whereby an emulsion fuel 12 having an ultra fine particle size and high mixture density is produced. According to the above configuration, cavitation can be extremely efficiently generated. The following technique is disclosed: a technique for producing various types of liquid mixture having an ultra fine particle size using the cavitation efficiently.