Automatic Transfer Switch (ATS) systems are designed to provide seamless and reliable switching between primary and backup AC power sources. These systems are commonly used to ensure uninterrupted power supply to critical loads, such as data centers, hospitals, and industrial facilities. The process of switching between primary and backup power sources seamlessly involves several key components and steps:
Sensing: ATS systems continuously monitor the voltage and frequency of both the primary and backup power sources. When the primary power source experiences an outage or a voltage/frequency deviation outside of acceptable limits, the ATS detects the issue.
Decision Making: Once a power source issue is detected, the ATS control logic determines the appropriate action based on preconfigured priorities and settings. It evaluates whether the backup power source is within acceptable limits and ready to take over.
Source Selection: If the backup power source is determined to be within acceptable limits and ready to provide power, the ATS initiates the switching process. It sends signals to the necessary components to disconnect the primary power source and connect the backup power source to the load.
Break-Before-Make Transition: To ensure safety and prevent electrical disturbances, many ATS systems use a "break-before-make" transition. This means that the connection to the primary power source is broken before the connection to the backup power source is established. This eliminates the risk of creating a short circuit or overloading the backup source.
Mechanical or Electronic Switching: ATS systems can use mechanical or electronic switches to make and break the connections between power sources. Mechanical switches often use solenoids or motor-driven mechanisms to physically move contacts. Electronic switches, such as solid-state relays, can achieve rapid and precise switching without moving parts.
Synchronization: In cases where the backup power source is a generator, synchronization between the generator and the load's electrical system is crucial to avoid phase and frequency mismatches. Synchronization controls ensure that the backup source seamlessly takes over without causing disruptions to the connected equipment.
Load Transfer: Once the backup power source is synchronized and stable, the ATS completes the transfer by connecting the load to the backup source. The transition happens quickly, typically within milliseconds, to maintain uninterrupted power supply.
Monitoring and Reversion: After the load has been successfully transferred to the backup power source, the ATS continues to monitor the primary power source. Once the primary source is restored and meets acceptable voltage and frequency criteria, the ATS can initiate a reversion process. This involves reversing the switching sequence to return the load to the primary source while ensuring another seamless transition.
It's important to note that the specific design and operation of ATS systems can vary based on the manufacturer, application, and requirements of the installation. The goal of these systems is to ensure the reliability and continuity of power supply during power source disturbances or outages.