Which factor must be considered when selecting overcurrent protection devices for a motor control circuit?

When selecting overcurrent protection devices for a motor control circuit, the rated full-load current of the motor is a crucial factor to consider. This is because the rated full-load current represents the maximum amount of current that the motor will draw when operating at its rated capacity. Overcurrent protection devices, such as circuit breakers or fuses, are designed to protect the motor from excessive currents that can potentially cause overheating, damage, or failure.

By ensuring that the overcurrent protection device is rated appropriately according to the full-load current, you create a safeguard against conditions that could lead to a motor failure while allowing for normal operation during startup and under full load. The proper sizing of these devices aids in maintaining the longevity and integrity of the motor and its associated components.

Factors like starting torque, ambient temperature, and voltage drop are also important in motor control applications but do not specifically dictate the sizing of overcurrent protection devices. Starting torque impacts the initial performance of the motor, while ambient temperature can affect the motor's efficiency and heat dissipation. Voltage drop is related to the electrical characteristics of the circuit but does not directly influence the selection of overcurrent protection. Thus, focusing on the rated full-load current ensures that the protective device appropriately matches the motor’s operational profile.