Description:
An Automatic Change Over Switch (ACOS), also known as an Automatic Transfer Switch, is an electrical device used to automatically switch a load between two power sources, typically the main utility supply and a backup generator or inverter. It is designed to ensure continuous power supply without manual intervention. The switch consists of sensing circuits, control relays, contactors, and interlocking mechanisms that prevent both power sources from being connected at the same time. ACOS units are commonly used in homes, hospitals, industries, and commercial buildings where power reliability is critical.

Operation:
The operation of an Automatic Change Over Switch begins with monitoring the main power supply. When the system detects a power failure, voltage drop, or abnormal condition in the main supply, it sends a signal to disconnect the load from the main source and connect it to the backup source (such as a generator). Once the main power is restored and stable, the switch automatically transfers the load back to the main supply and disconnects the backup source. This process happens quickly and safely, ensuring minimal interruption to connected equipment while preventing electrical faults like backfeeding or short circuits.