The in-flight melting technology with multi-phase alternating cut-rent (AC) arc was developed for the purpose of saving energy and shortening production cycle for glass industry. The 6-phase arc and 12-phase arc were used to investigate the in-flight melting behavior of soda-lime and alkali-free glass powders. Results showed that the vitrification degree of raw materials and the shrinkage of particle diameter increased with the increase of input power. The higher melting temperature and viscosity were responsible for the lower vitrification degree of alkali-free glass powders. Compared with 6-phase arc, 12-phase arc improved the vitrification degree of raw material for the longer residence time and higher plasma temperature under the same transformer current. The high vitrification degree achieved in short time indicated that the new in-flight melting technology with multi-phase ac arc would be a promising method for energy conservation in glass industry. (C) 2007 Elsevier B.V. All rights reserved.