What are the functions and differences between STS and ATS?

I. Definitions of STS and ATS

1. Static Transfer Switch (STS) is a power switching device based on electronic circuits, mainly used to achieve fast and seamless switching between two independent AC power sources. Its core components include an intelligent control board, high-speed thyristors, and circuit breakers.

2. Automatic Transfer Switch (ATS) is a mechanical power switching device, mainly used in emergency power supply systems to automatically switch the load circuit from one power source to another backup power source. Its switching actuation component is usually a contactor or circuit breaker.

II. Functions of STS and ATS

1. Functions of STS

(1) Fast Switching An STS can quickly switch to a backup power source when the main power source fails. The switching time is usually no more than 8 milliseconds, and can even reach 1/4 cycle (≤5 milliseconds). This fast switching capability ensures the uninterrupted operation of precision electronic equipment and avoids data loss or equipment damage due to power interruption.

(2) High-Reliability Power Supply An STS is suitable for occasions with extremely high power quality requirements, such as data centers, communication base stations, and laboratories. It can provide dual-bus power supply for single-power-supply loads, enhancing the redundancy of the power supply system.

(3) Multi-power compatibility: STS can achieve seamless switching between UPS and UPS, UPS and generator, UPS and mains power, and mains power and mains power, providing reliable power support for equipment in complex power environments.

2. Functions of ATS

(1) Emergency standby switching: ATS is mainly used in emergency power supply systems. When the main power supply fails, it automatically switches to the backup power supply to ensure the continuous operation of important loads. Its switching time is usually over 100 milliseconds, suitable for loads that are not sensitive to short-term power outages, such as lighting and motors.

(2) Mechanical structure reliability: ATS uses mechanical contact switching, which has strong anti-interference ability and high switching success rate. Its structure is simple, maintenance cost is low, and it is suitable for large load switching.

(3) Wide application: ATS is widely used in industrial production, data centers, hospitals, and other occasions that require continuous power supply, especially performing well in scenarios where switching speed requirements are not high.

III. Differences between STS and ATS

1. Switching Speed

STS: Extremely fast switching speed, typically between 5 and 8 milliseconds, suitable for devices sensitive to power interruptions.

ATS: Slower switching speed, typically over 100 milliseconds, even reaching 1.5 seconds, suitable for loads insensitive to brief power outages.

2. Switching Method

STS: Uses electronic switches (high-speed thyristors) for switching; the switching process is "break first, then make," enabling seamless switching.

ATS: Uses mechanical contacts (contactors or circuit breakers) for switching; the switching process relies on mechanical action and may involve brief power outages.

3. Application Scenarios

STS: Suitable for applications with extremely high power quality requirements, such as data centers, communication base stations, and precision instruments.

ATS: Suitable for applications insensitive to brief power outages, such as industrial production, hospitals, and lighting.

4. Reliability

STS: The electronic switching method makes it more sensitive to electromagnetic interference and temperature factors, but it offers higher switching speed and safety.

ATS: Mechanical contact switching provides stronger anti-interference capabilities, but may lead to malfunctions due to contact wear and overheating.

5. Cost and Maintenance

STS: Higher equipment cost, but relatively simpler maintenance.

ATS: Lower equipment cost, but the mechanical structure requires regular maintenance.

STS, with its advantages of fast switching and high-reliability power supply, is suitable for precision equipment sensitive to power outages; while ATS, with its reliable mechanical structure and lower cost, is suitable for ordinary loads not sensitive to brief power outages. In practical applications, the appropriate choice between STS and ATS should be made based on load characteristics, power supply environment, and budget to ensure the stable operation of the microgrid system and the reliability of power supply.