A 4-pole Automatic Transfer Switch (ATS) is an electrical device that automatically switches a 3-phase load between two power sources—typically the main utility and a backup generator. The 4th pole is used to switch the neutral wire, ensuring complete isolation between the two power systems.
Key Benefits & Functions
Neutral Switching: Unlike 3-pole switches, a 4-pole ATS switches all three phases plus the neutral. This is critical for systems where the backup source is a "separately derived system" (e.g., specific generator grounding setups) to prevent unwanted ground loop currents.
Automatic Operation: It detects power failure or voltage fluctuations and signals the backup generator to start. Once the generator's power is stable, the ATS transfers the load.
Safe Isolation: It prevents "backfeeding" by ensuring the two power sources