How Does An Automatic Transfer Switch Work？

With the continuous improvement of science and technology and economic level, people's lives and work cannot be separated from electricity. Safe and stable power supply is becoming more and more important to people. So how to ensure that there will be no power outages?
The backup emergency power supply system has emerged. It can ensure that when the main power supply fails, it can intervene instantly and take over the power supply. Among them, its key equipment-automatic transfer switch must be mentioned.

The automatic transfer switch can automatically switch to the backup power supply when the main power fails to ensure uninterrupted power supply.
The core working principle of ATS (automatic transfer switch) is actually divided into three key steps:
1. First, the control unit will always monitor the voltage, frequency and other parameters of the main power supply.
2. Once a power outage, voltage instability or frequency abnormality is detected, the switching program will be started immediately.
3. Next, the switching unit will start working. It will disconnect the main power supply through mechanical contacts or electronic switches, and then connect the backup power supply.
This switching process is very fast, usually only 100 milliseconds to a few seconds to complete.
In order to ensure safety, the ATS switch is also equipped with multiple protection measures, such as mechanical interlocking devices, which can prevent the main and backup power supplies from supplying power at the same time and causing short circuits. Some models also support zero line overlapping switching to further shorten the power outage time.

ATS switch mainly consists of four parts:
1. Control unit, responsible for monitoring and issuing instructions.
2. Switching unit, performing specific operations,
3. Power supply unit connects to reserve power supply,
4. Load unit connects to equipment that needs protection.

Classification of automatic transfer switch:
In actual use, ATS switch has three common working modes:
1. Self-investment and self-payment mode: The most common is the self-investment and self-payment mode, which will automatically switch back after the main power is restored.
2. Self-investment and non-self-payment mode: manual operation is required to switch back to the main power supply,
3. Parallel mode: the main power supply and backup power supply can be powered at the same time.

According to different switching methods, ATS switches are mainly divided into two types:
1. PC level. It uses mechanical contacts with a switching speed between 100ms and 3 seconds, which is suitable for industrial motors and lighting systems.
2. CB level integrates circuit breakers, with a slightly slower switching speed, but safer, suitable for ordinary commercial buildings. This type of equipment is widely used in places with extremely high power supply requirements, such as hospitals, operating rooms, data centers, and financial systems. If used with an uninterruptible power supply, it can even achieve zero-interruption switching.

 Critical power facilities: such as hospitals, data centers, and industrial production lines. In these places, power outages may lead to serious consequences, such as medical equipment downtime, data loss, or production interruptions. ATS can quickly switch to backup power when the main power fails to ensure the continuous operation of critical equipment.
Infrastructure: such as transportation facilities such as airports, railway stations, and subway stations, as well as communication base stations. The power supply of these facilities is critical to operational safety, and ATS can ensure their normal operation when the main power fails.
Commercial and residential areas: such as shopping malls, office buildings, and residential areas. In these places, power outages can affect commercial activities and residents' lives. ATS ensures the continuity of power supply and guarantees normal operation.

In summary:

Automatic transfer switchgear is mainly used in emergency power supply systems, which automatically switches the load circuit from one power supply to another (backup) power supply to ensure continuous and reliable operation of important loads. Therefore, it is often used in important power consumption places, and its product reliability is particularly important. Once the conversion fails, it may cause one of the following two hazards: short circuit between power sources or power failure of important loads (even short power outages), the consequences are serious, which will not only bring economic losses (production suspension, financial paralysis), but also may cause social problems (life and safety are at risk). Therefore, industrially developed countries have listed the production and use of automatic transfer switch electrical appliance