What type of protection does a manual across-the-line three-phase motor control provide?

A manual across-the-line three-phase motor control primarily provides overload protection. This type of control directly connects the motor to the supply voltage, allowing it to operate at full line voltage. The main objective of an overload relay, which is typically included in such systems, is to monitor the motor's current. If the current exceeds a specified level—indicating that the motor is overloaded—it will trip and disconnect the motor to prevent damage.

While disconnect protection could be provided as part of the manual control setup, the key feature of an across-the-line starter is its integration of overload protection to prevent thermal failure of the motor under excessive load conditions. Short circuit and ground fault protections are additional safety features that would typically require separate devices or circuitry beyond the manual control itself, making them less relevant in the context of this question. Thus, the emphasis on overload protection aligns with the main function of the described control system.