Which type of motor starting method should not be used for long startup times or high inertia loads?

The correct response highlights the fact that part winding starting is not suitable for long startup times or high inertia loads due to its design and operational characteristics. Part winding starting involves energizing only one half of the winding at the start, which limits the starting torque available. This method is typically more effective for lower inertia loads where the required starting torque can be achieved without overwhelming the motor or the power supply. For high inertia loads, the initial torque needs are generally higher to overcome the inertia and get the load moving.

Using part winding starting in such applications may result in insufficient torque, leading to sluggish starts or potential motor stalling. Therefore, this method is reserved for specific scenarios where the load characteristics align more closely with its capabilities, particularly for lighter loads.

In contrast, the other starting methods mentioned, such as soft starting, direct on-line starting, and wye delta starting, are designed to manage higher starting torques and longer startup conditions effectively. Soft starters gradually ramp up the motor voltage, allowing for smoother starts with reduced mechanical stress. Direct on-line starting applies full voltage immediately, providing maximum torque when needed. Wye delta starting reduces starting current and torque by starting in wye configuration before switching to delta, making it more adaptable for higher inertia applications