Which statement is true about the thermal overload unit?

The statement regarding the thermal overload unit being able to adjust current ratings is correct. Thermal overload units are designed to protect electrical equipment, such as motors, from damage due to excess current caused by conditions like overheating or jams.

One of the key features of these units is that many allow operators to adjust the current settings according to the specific ratings of the motor or device they are protecting. This adjustability ensures that the overload unit can be tailored to provide optimal protection based on the anticipated operational current of the motor, enhancing the efficiency and safety of the system.

In contrast to this, other options suggest characteristics that do not apply to thermal overload units. For example, stating it is unaffected by electrical parameters overlooks the fact that thermal overload units must interact with the electrical characteristics of the equipment to operate effectively. Saying it is used only for single-phase motors is misleading, as thermal overloads can be used for three-phase motors as well. The notion that it creates a delay in operation may confuse the immediate response needed in a real-time overload situation, where the unit is designed to react quickly to protect the motor or device.