Sun industries presentes auto transformers for on-line starting of motors which are simple and economical. It offers maximum starting acceleration and torque. Auto transformer overcomes the two major limitations of on-line starters - high starting current and high starting torque. The major advantage of this method of starting motors are: best for hard to start loads, adjustable starting torque, can be used with any standard motors and less strain on the motor. Auto-transformer starting uses an auto-transformer to reduce the line voltage during the starting period. The auto-transformer voltage taps provide a choice of three different starting currents and torques, depending on the load requirements. In this system, the first step is connected to one of the reduced voltage taps, which results in a reduced starting current and torque. After a preset time delay, the second step applies full rated voltage to the motor for normal operation. For the same value of line current drawn during the starting period, motors with auto-transformer type starters/panels deliver the maximum starting torque when compared to other type of starters.
