Motor starters protect motors from an under voltage condition. If the voltage of the power supplied to the motor drops below 65% of the design voltage, a coil disconnects the motor from the supply voltage. It is used to provide automatic control for motors. Motor starters can be either manual or magnetic. Manual starters are used only for small fractional horsepower motors. Manual starters may be toggle, selector, or push button switches. They are used for integral motors. They use an auxiliary circuit within the starter to energize a magnetic coil, which closes the starting switch.
Motor Starting Auto Transformers with fixed tapping are used in auto transformer type of starters to reduce the voltage across the motor terminals while starting. This transformer uses high quality E.I laminated silicon steel processed from state of the art modern punching facilities, high quality enamelled/fibre glass covered copper or aluminium wires of 1 PEW and EIW grades withstand temperatures up to 155°C & 180°C respectively and high quality polyester varnish for good bonding & high dielectric strength, which reduces electrical leakage and noise. These transformer features open frame construction, three coil design and class F Insulation. Its primary function is to limit inrush current and starting torque in AC motors under starting or locked rotor conditions. This eliminates the problems associated with line voltage drop, resulting from high inrush currents.