Application of inverter-driven jet-fans to the high-way tunnel

The advantages of the variable speed drive of jet-fans have been known from more than twenty years ago. But at present, all jet-fans of the world have been driven at constant speed by the utility power sources. This is because, to realize the induction motor drive through the long cable, following difficult problems must be solved. These problems are the switching surge problem which deteriorates the motor insulation, the EMI problems to the tunnel electronics equipment, the axial current of motors deteriorates the shaft bearings, the leakage current which cause malfunction of the leak current relay and the voltage drop of the long cable causes the stall of the motor at high speed range. To solve these problems, we got the sponsorship of the government (MLIT) and started the developments in 2007. And in December 2010, we put the variable speed drive of jet-fans into practical use. In this paper, the principle of the inverter system for jet-fans, and test results on the actual road tunnel will be presented.