On starting the motor is connected to the tappings of the auto transformer. An autotransformer starter reduces inrush current by using a transformer in the line just ahead of the motor to step down the voltage applied to the motor terminals.
Auto Transformer Starter
Autotransformer motor starter wiring diagram. Autotransformer motor starter duration. There are various starter used to start induction motor like direct online starte r soft starter s tar delta starter auto transformer starter auto transformer starter is used for large hp motor. Star delta connection duration. The motor starts at the voltage reduced by the transformer with a correspondingly smaller current. The figure a shown below shows the condition when the motor is directly switched on to lines and the figure b shows when the motor is started with the help of auto transformer. Let z e10 is the equivalent standstill impedance per phase of the motor referred to the stator side.
When the setting time on the timer has expired the autotransformer is bypassed. Hence another starting method is used to start three phase induction motor called an autotransformer starter. Star delta starter control circuit diagram. By reducing the voltage the current drawn from the line is reduced during start up. V 1 is the supply voltage. In contrast to the star delta connection only three motor leads and terminals are required.
Auto transformer starter motor starters. Transformer contactor k2m and star contactor k1m are closed. Theory of auto transformer starter. Auto transformer starter can be used for both stardelta connected. Squirrel cage induction motor started on full line voltage using d o l starter as a starting method draw very large starting current which can damage motor winding and also create a current surge on the power system. Autotransformer starter working wiring and control diagram.
Gallery of Autotransformer Motor Starter Wiring Diagram
