An automatic transfer switch is a smart switch that detects when power is lost in the primary power source to which it is connected. Subsequently, it transitions autonomously to a secondary or emergency power supply. A generator, backup utility grid, or solar system are examples of the power sources the automatic transfer switch (ATS) typically connects to.

For instance, in a grid-connected PV system, a solar ATS will switch from the grid to the solar battery and vice versa when the grid goes down. This guarantees there won’t be any downtime because of a power outage or other issues, which could result in losses for your company and other problems.

Applications for Automatic Transfer switches (ATSs) range from solar power to emergency power systems, including generators and UPSs. Continue reading to know more about these switches.

Automatic Transfer Switch Design and Primary Parts

Different designs for automated transfer switches exist depending on what the application requires. Single-phase and three-phase ATS are the two most popular varieties. These will also have varying quantities of poles.

Like a firebox, the size of an automatic transfer switch also varies based on its intended use. Large transfer switches are frequently utilized in industrial environments and have draw-out mechanisms or enclosures to allow for safe repair. However, smaller automatic transfer switch sizes are more typical in residential applications. This kind is primarily categorized as a low-voltage automatic transfer switch (below 1KV) and is frequently simple to install.

Even though designs differ, automatic transfer switch assemblies typically consist of the following primary components:

  • The “brain” of the ATS is the logic controller. It regulates the switching process and keeps an eye on the power supplies.
  • The apparatus that alternates power sources is known as a switching mechanism. It could use solid-state technology or be a mechanical switch.
  • Control and contacts are additional components of an automatic transfer switch.

The Function of an Automatic Transfer Switch

Primary Purpose: Two-way Power Conversion

An automatic transfer switch appliance automatically switches one or more load circuits from one power source to another. It includes a transfer switch appliance (or more) and other required appliances.

Here is a step-by-step process showing how an automatic transfer switch in a grid-connected solar or generator backup system operates:

  • When there is a utility grid power outage (frequency or voltage dips), the automated technology system (ATS) instantly senses the change and either connects to solar power or triggers the generator to start. (The switch shifts the load to the generator as soon as it reaches its peak speed and stability.)
  • The frequency and voltage of the grid revert to normal. When power returns, the ATS logic controller detects it and returns the load to the utility grid.
  • In a generator backup system, the switch will also tell the generator to shut down; however, this usually happens after a delay to guarantee grid stability and give the generator time to cool down.

While autonomous operation is the goal of an automatic transfer switch, many switches offer remote switching for human or semi-automated control. Because of this, users can override the auto function as needed.

Manual VS Automatic Transfer Switch

Automatic or manual transfer switch equipment is available. A manual or non-automatic control requires an operator to physically operate the switch, whereas an automatic transfer switch doesn’t. Comparing automatic transfer switches to manual ones reveals several benefits.

Automatic switches not only save the operator from having to be present during a power loss or switchover, but they also operate more quickly. This is because they have sensors and logic controllers installed, enabling them to swiftly switch power sources when needed. Furthermore, features like load shedding, generator exercise clocks, and remote controls can be added to the ATS powerbox to increase flexibility and user-friendliness.

Extra Features—features for Safety

The two types of ATS automatic transfer switches are PC level and CB level. PC level ATSE solely carries out the dual power conversion function, while CB level ATSE additionally performs the overcurrent (short circuit) prevention function. CB Level ATSE is a product description and stereotype that, in the past, completed the power conversion function using a dual circuit breaker combination.

Advantages of Installing an Automatic Power Switch

Automatic transfer switches benefit your company as they boost productivity and security. You will get the following benefits when you select the appropriate switch for your needs:

Power Dependability

Your company will have serious problems if you cannot obtain electricity for whatever reason. Although a generator can help with this to some extent, if there isn’t a transfer switch, you will still need to manually connect your backup generator to the operation you want to resume. This process not only takes a long time and results in downtime but also restricts the generator’s capability. Not to mention that the delay can be detrimental to your machines. Therefore, an automatic transfer switch helps you avoid these complications by automatically switching on your energy backup during an outage.

Operation Simplification

Upon installation, the automatic transfer switch will choose the automated power supply’s specific mode of operation. Everything from your lighting to your HVAC system, industrial equipment, and even refrigerators might fall under this category. This procedure enhances generator functionality and makes power restoration much simpler.


There are risks associated with handling any power source. Abrupt power outages can cause injuries to workers, and handling manual generator connections might go disastrously wrong, especially at night! By taking care of everything on its own, the transfer switch removes the risk of power interruptions.

The Sum Up

An automatic transfer switch (ATS) automatically switches the power supply from the main source to a backup source when it detects a malfunction or outage in the primary source. The auto transfer switch has a long service life, no noise, tiny impact, easy and dependable operation, and a simple design. These switches are appropriate for lighting circuits in high-rise buildings, retail centers, banks, and commercial buildings where power outages are not expected to occur for extended periods.