Automatic Transfer Switches: Function, Use, and Maintenance

Automatic transfer switches, also known as ATS, serve an important function in power systems. An ATS monitors two power sources and automatically switches between them in the event of failures or outages. This ensures constant supply of power to critical loads with minimal interruption.

Function and Operation

An ATS continuously monitors two power sources, typically a mains utility source and a backup generator. When the primary power source fails or drops below a set voltage threshold, the ATS immediately switches the load to the secondary source within milliseconds. When the primary power returns to normal parameters, the ATS will automatically switch the load back.  

This dual power capability offers resilience and reliability for critical systems that require constant uptime. ATS units are commonly used in data centers, hospitals, factories, and other facilities with sensitive equipment.

Use and Installation

When installing an ATS, there are several considerations to optimize performance:

Size - The ATS must be rated to handle the total load of the connected circuit. Undersized units can fail prematurely.

Connections - All wiring from the power sources and loads must be properly secured and in accordance with local electrical codes.

Grounding - Both power sources and the ATS unit itself must have a proper earth ground connection to minimize transient voltage surges.

Distance - The ATS should be installed as close as possible to connected loads for minimal voltage drop.

Maintenance and Inspection

To ensure proper long-term operation, ATS units require periodic inspection and maintenance:

Calibration - Voltage and timing calibrations should be checked annually to verify transfer thresholds and switching speeds are within specifications.

Contact Inspection - The internal switch contacts must be visually inspected for signs of heat damage, corrosion or contamination.

Testing - The ATS should be manually exercised at least once a year to verify it can properly transfer the load between sources. Any issues can then be diagnosed and repaired.

Replacement - Depending on operating conditions and load cycling, ATS units typically have a service life of 10 to 15 years before components degrade and fail.

With proper installation, use, and scheduled maintenance, automatic transfer switches can reliably provide backup power for sensitive systems and ensure critical operations continue during utility outages. Regular inspections and timely replacement of worn parts are crucial to sustain optimal performance of ATS units over their operational lifetime.