What is a Server ATS Automatic Transfer Switch?

An ATS (Automatic Transfer Switch) is an automatic power switching device for various equipment, such as data centers and servers. PCBONLINE provides one-stop OEM PCB manufacturing for server ATS, and in this blog, we will introduce what a server automatic transfer switch is.

Please note that a server ATS is a single module, which is essentially a PCBA (printed circuit board assembly). So we also introduce the PCBA for server ATS in this article.

What Is an Automatic Transfer Switch?

First, let's see what an automatic transfer switch is. It allows seamless transfer between a primary power source and a backup power source.

When the main power fails or becomes unstable, the ATS automatically switches to the backup source within milliseconds to seconds, ensuring a continuous power supply for servers and data centers.

In server or data center environments, an ATS not only automatically switches between dual power inputs. It also provides power redundancy and prevents server downtime due to a single power path failure.

For example, each rack server has two power supplies connected to PDU-A and PDU-B. If one PDU loses power, the ATS automatically switches to the other power feed to keep the server running.

Automatic transfer switch structural types

An ATS can be used for different applications, such as data centers and servers. Its structural designs include modular and system-level. For a server, its automatic transfer switch is a modular one, namely, a single PCBA.

Modular (rack-mount) ATS is in a compact size, usually 1U or 2U rack-mounted. It is designed for a single or small group of servers and used in rack-level power distribution.

Its structure usually contains 2 power inputs (Input A / Input B), 1 power output, and an internal circuit that includes power sensing and transfer control (relay or solid-state switch).

System-level ATS (switchgear or distribution cabinet) is built from multiple modules such as contactors, controllers, and monitoring units. It is installed at the main distribution board of a data center or building.

It handles high current capacity from 100A to 1600A+, and includes control logic, delay functions, interlocks, and alarm monitoring.

A system-level ATS usually contains a main utility + backup for inputs, feeds downstream PDUs or UPS systems for outputs, and microprocessor-based controllers with protection and monitoring functions for control.

To sum up, an ATS can be either a single module or a multi-module system, depending on the application level. At the server or rack level, it's a compact rack-mount module. At the facility or distribution level, it's a larger system composed of multiple modules. There's a comparison table for you for a straightforward understanding of the automatic transfer switches.

When learning about the automatic transfer switch, it is important to understand its relationship with UPS. ATS addresses the problem of "switching between power sources." UPS addresses the problem of "power continuity and quality."

They are often used together: utility power → ATS → UPS → servers or dual UPS inputs → ATS → servers.

What is a Server Automatic Transfer Switch?

From the above, we learned that the automatic transfer switch used in servers is a rack-mount single module.

Specifically, a server ATS is a medium-sized PCBA, 1U or 2U in height, and 19-inch rack standard width. Its main components include dual power inputs, output connectors, status LEDs, and alarm/communication ports.

This rack-mounted ATS, a main PCBA (Printed Circuit Board Assembly), integrates these functional sections:

The ATS hardware consists of one main PCBA, and sometimes a small interface board for connectors or communication.

Why is one PCBA enough for building a server automatic transfer switch? Because rack-level ATS devices usually handle relatively small loads.

A server ATS features:

• Rated current: 10A to 32A
• Single-phase or dual-phase
• Only one output line (one-in, one-out design)

These functions can easily be implemented on a single mid-sized power PCBA (typically around 20 × 15 cm or smaller).

There is no need for large electromagnetic contactors or power transformers. So the compact design is achievable and efficient in both space and heat management.

When multiple modules are needed? Large-capacity ATS systems (hundreds or thousands of amps), such as those installed in main data center distribution cabinets, require multiple PCBAs.

To sum up, the automatic transfer switch used in server environments is a compact, rack-mounted single-module device. Internally, it mainly relies on a single PCBA to handle all essential functions, including sensing, control, switching, and communication.

Printed Circuit Board Assembly for Server ATS

The server rack-mount ATS PCBA is a high-power circuit board that requires wide traces and thermal design, but generally does not need HDI PCB. Its main components focus on MCU control, relays/solid-state switches, voltage/current sensing, protection, and status/display/communication interfaces.

The size and requirements of a PCBA for the server automatic transfer switch are below.

• Size: Medium-sized, around 15–25 cm × 10–20 cm
• Power rating: 10–32A single-phase, or small three-phase applications
• High-power design considerations: Copper thickness usually 2–3 oz to carry large current, wide current traces, heat sinks for SSR/MOSFETs, thermal copper planes, electrical clearance, and insulation to prevent short circuits.

A high-power ATS PCBA's core functions are power switching, relay/solid-state control, and MCU logic， and it requires no ultra-fine pitch ICs or extremely dense traces. Usually, a standard 2–4 layer PCB is sufficient for a server ATS.

If communication modules (SNMP/Ethernet, LCD display) are included, a few signal layers may be added.

How about the key components of a server automatic transfer switch? The components in its various function zones are below.

Control & logic

• MCU/microcontroller (monitors main/backup power and controls switching)
• Clock/timer circuits (for transfer delay and lockout)
• Power management ICs (for MCU and low-voltage drivers)

Sensing & sampling:

• Voltage/current sensing circuits (resistor dividers or current shunts)
• Comparators/operational amplifiers
• ADC (if not integrated in MCU)

Switching execution:

• Solid-state relays (SSR) or small electromagnetic relays
• Small power contactors for higher current
• Optional power modules with MOSFET or IGBT drivers

Protection:

• Fuses/PTC resettable fuses
• TVS diodes for overvoltage protection
• MOVs for surge protection (optional)

Status display & communication:

• LED/LCD indicators
• Communication interfaces: RS485, CAN, SNMP

Input/Output Connectors:

• Power input/output terminals
• Signal connectors for monitoring or alarms

For a clear summary, you can check the table below of PCBA for server ATS.

Partner with PCBONLINE for Turnkey PCBA of Sever ATS

Since our foundation in 2005, PCBONLINE has been committed to turnkey OEM PCBA. We focus on PCBA manufacturing for server automatic transfer switches, medical, automotive, industrial controls, and AIoT.

Our turnkey OEM PCBA services offer:

• Turnkey PCBA manufacturing: From PCB prototypes and testing to mass PCBA and box-build assembly, our PCB assembly services are custom and one-stop.
• Complete procurement: We source and customize enclosures, cables, and accessories from reliable suppliers.
• Engineering support: We check enclosure and accessory designs for compatibility with your PCBA and can suggest design changes.
• Free DFM/DFT: We provide free Design for Manufacturability (DFM) and Design for Testability (DFT) checks to ensure that designs are optimized for a smooth production process.
• Quality assurance: IPC-A-610 Class 2/3, automotive-grade or industrial-grade inspection standards.
• Turnkey delivery: From PCB fabrication to final product packaging and shipping.

Whether you need turnkey OEM PCB assembly for server automatic transfer switches, AI hardware, IoT devices, medical-grade products, or automotive modules, we can deliver the PCBAs of high quality and in time, meeting any of your project requirements. To get a quote for your PCBA project, email us at info@pcbonline.com.

Conclusion

The server automatic switch is a single-module but high-power device, and only a 2 to 4-layer PCBA is enough for building it. With more than 20 years of electronic manufacturing experience in turnkey OEM PCBA, we are ready to check your Gerber and provide turnkey services for your server ATS project. Contact PCBONLINE today!