In an electrical control circuit, when is an interval relay typically activated in a sequence?

In an electrical control circuit, an interval relay is typically designed to be activated after a predetermined delay. This means that, once the relay receives a signal (like pressing a START button), it will wait for a specified period before turning on or allowing current to pass through. This functionality is crucial in various applications, such as in processes that require a certain time to elapse before initiating an action, helping to prevent components from being activated instantly or unnecessarily.

This design allows for time-based control, which can increase safety or ensure that system parameters have stabilized before the next stage of operation begins. For example, in automated systems, this can prevent a machine from starting too quickly after being powered on, allowing time for the systems to calibrate or for safety checks to complete.

In contrast, the other options reflect scenarios where an interval relay would not be appropriate. Pressing the START button would typically trigger immediate actions or other relays without the delay characteristic of an interval relay. Activating based on both M1 and M2 being on relates more to a logic function rather than a timing delay. Finally, activation upon system shutdown does not align with the primary function of interval relays, which is focused on timing rather than the cessation of operation.