What are two major disadvantages of an autotransformer starter with an autotransformer in each phase of the three-phase supply?

When considering the use of an autotransformer starter for three-phase supplies, the major disadvantages often highlight the financial implications and the transition method during starting.

The primary disadvantage associated with cost refers to the expense involved in implementing autotransformer starters compared to other types of starters. Autotransformer starters can be more expensive due to the complexity of their design and the need for additional components to achieve the desired voltage reduction for soft starting an induction motor.

Open transition refers to the method of transitioning from the reduced voltage provided by the autotransformer to the full voltage of the supply during the starting sequence. In an open transition, there is a brief period where the motor is disconnected from the power source as it switches from the autotransformer circuit to the main circuit. This can cause a momentary interruption in the power supply, leading to potential issues in applications where a continuous power supply is critical. Such interruption can also lead to mechanical stresses or other operational challenges in the driven systems.

Collectively, these two disadvantages—high cost and the open transition method—effectively outline the drawbacks of utilizing an autotransformer starter in a three-phase supply scenario. The other options do not accurately capture these relevant disadvantages when focused on the context of autotransformer starter applications