What is the term for a momentary connection of separate synchronized AC power sources to avoid interruption before the transfer of power?

The term that describes a momentary connection of separate synchronized AC power sources to prevent interruption before switching power is known as "Seamless Transfer." This process is critical in applications where maintaining a continuous power supply is essential, such as in marine environments or critical infrastructure.

Seamless transfer allows for the synchronization of multiple power sources, ensuring that there is no drop in voltage or frequency during the switch from one source to another. This is particularly important in systems where equipment could be sensitive to any brief loss of power, which could lead to malfunctions or damage.

The other options do not capture this specific operation effectively. While power relays are devices that control electrical circuits and can be involved in the transfer process, they do not refer specifically to the momentary connection aspect. Load switching pertains to controlling the power delivered to different loads rather than the transfer process itself. Power backup typically refers to systems designed to provide alternative power sources during outages, but it does not imply the same immediacy or synchronization that seamless transfer entails.