How does ATS know when the mains power is out?

On that stormy night when the power went out, you were probably sound asleep. Suddenly, the mains power went out, and just seconds later, the Generator automatically roared to life, and the lights came back on.

This seamless coordination is all thanks to the generator set's "brain"—the ATS (Automatic Transfer Switch). But have you ever wondered: since it has neither eyes nor ears, how does it know the mains power is down?

1. 24-Hour Monitoring

The ATS is not just a simple switch; it integrates a high-precision voltage monitoring module. Like a doctor who never rests, it constantly monitors the mains power supply via signal lines.

Specifically, it monitors the three-phase voltage (A/B/C phases) of the mains power line in real time. As long as the mains power is within the normal range (e.g., 380V ±15%), the ATS remains silent, allowing the mains power to supply power.

2. More Than Just a Power Outage: It's More Thorough Than You Think

The ATS's judgment criteria are extremely strict. A power outage isn't limited to a complete lack of power. The following situations will also be classified as "mains power failures":

* Undervoltage/Overvoltage: Voltage suddenly drops below a specified value (e.g., below 300V), or voltage spikes.

* Phase Loss: One of the three live wires suddenly loses power (this is fatal to downstream motor equipment).

* Frequency Abnormality: Excessive fluctuations in mains power frequency.

3. A few seconds of "thinking" to prevent false alarms

You might ask, "If the mains power only flickers briefly (0.5 seconds) and then immediately returns to normal, will the generator still start?"

Of course not. A smart ATS has an internal delay confirmation logic (usually configurable from 0-10 seconds).

When a mains power abnormality is detected, it first "counts down." If the mains power returns to normal after a few seconds, it treats it as if nothing happened; if the mains power is still abnormal after the countdown ends, it will determine it as a "real power outage" and immediately send a start signal to the generator set.

The ATS is the "sentinel" of the power backup system. It precisely commands the generator set to engage by detecting voltage changes and filtering instantaneous fluctuations.

Friendly reminder: The controllers and relays inside the ATS are precision electrical components. It is recommended to perform a professional "simulated power outage test" annually to ensure its sensitive detection in critical moments.

Shandong Supermaly Generating Equipment Co., Ltd. provides professional ATS cabinet maintenance and upgrade services, ensuring flawless power switching.