The autotransformers are used for AC 50HZ at rated voltage 308V. The infrequent partial voltage starting of the three-phase squirrel-cage induction motor of power of between11 and 315 (KW) is to minimize the impact of the motor on the transmission network at the time of startup.

It adopts F and H-grade insulation system, and maintains splendid electrical and mechanical performance throughout the life of the autotransformer. The F and H-grade materials are anti-aging, anti-shrinkage and anti-compression with particularly strong elasticity, thus ensuring the compact structure of the transformer after several years of use and the capability to the pressure of short-circuit. The entire autotransformer is macerated is macerated in Class H maceration paint under vacuum pressure (VPI), and is cured at high temperature in oven.