What are two reasons for using reduced voltage starting for three-phase induction motors?

Using reduced voltage starting for three-phase induction motors primarily serves two significant purposes: to limit mechanical shock and to reduce starting current.

When an induction motor starts at full voltage, it draws a high inrush current, which can be several times greater than the motor's rated current. This large current can create substantial mechanical stress on the motor’s components and the connected load, potentially leading to damage or misalignment. By employing reduced voltage starting methods, such as star-delta or autotransformer starting, the initial starting current is significantly decreased, which helps to mitigate mechanical shock on the motor and its associated equipment.

Additionally, reducing the starting current not only protects the motor but also lowers the voltage drop in the power supply system, enhancing system stability during the start-up period. This approach is crucial for maintaining the integrity of both the motor's operation and the electrical system it is connected to.

The other options do not emphasize these key effects of reduced voltage starting, making limiting mechanical shock and reducing starting current the primary advantages of this technique.