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TwinPower ATSs

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Coping With Loss

An Automatic Transfer Switch (ATS) enables critical equipment to have both a primary and a secondary power feed. By default, equipment is powered by the primary feed. If the primary power fails, the ATS automatically switches to the secondary power feed. This ensures that critical equipment is provided with power, even if the primary power feed fails.

Marway’s ATS products use a “break before make” switching mechanism. This technique ensures isolation of the two power feeds, and eliminates a requirement for the two power feeds to be phase synchronized. This type of auto transfer switching is used mostly when there is a UPS between the ATS and PDU, or for equipment which, though powered, may not be actively engaged in work 100% of the time, or would otherwise not lose functionality due to a power loss lasting just under 20 milliseconds.

Illustration showing how an ATS works when integrated with a PDU
An auto transfer switch has two power feeds, each from a different power grid, to provide alternate power to a PDU if the primary source fails. For some applications, it may be necessary to have a UPS between the ATS and PDU.

Standard or Custom

  • Standard models for 120 Vac and 208 Vac, 30 amps.
  • Integrated EMI filter and surge suppression.
  • Outlet types include 5-20, L5-20, L5-30, L6-30, C13, C19

There are several pre-designed models to choose from offering a variety of inlet types, power loads, controls, and outlets. In some cases, models include multiple outlets and other features to effectively be the ATS and the PDU in one unit.

As with all Marway products, we specialize in optimizing a design to incorporate the exact features needed for your application. For an auto-transfer switch, that could include extra control or monitoring, a unique mixture of outlet types, or power input signal conditioning.

a photo collage of several front panels of Marway TwinPower ATS products
True to Marway’s custom DNA, in addition to pre-designed units, the TwinPower products are available with customized inlet types, outlets, panel controls, etc.

When to Use an ATS

There are numerous possible scenarios, but it may help to contrast two basic scenarios to help explain when the ATS is a useful power management tool.

Let’s start with an example where an ATS is not typically needed—a rack of computer servers in a modern data center with completely redundant power grids in the building. Most modern servers feature dual power supplies. One power supply is connected to power grid A, and the other to power grid B. This setup has two power sources, and the equipment itself already has two power inputs. Since there’s redundancy built in from end to end, an ATS is not needed here.

Now, let’s consider a group of industrial equipment where each piece has a single power input (which is almost always the case). Whether the facility has dual power grids, or the installation simply requires alternative power supplied from two separate breaker panels, the equipment cannot accept the dual power sources. This is where the ATS comes in. The two power sources are connected to the ATS. The ATS is connected to, or incorporates, power distribution to each piece of equipment. If one of the power sources fails, the ATS performs the task of switching to the secondary source.

An illustration depicting power distribution schemes where an ATS is and is not suitable.
In the top scenario, an ATS is not needed since the equipment being powered already accepts two power sources. However, where equipment has only a single power inlet, the ATS provides the means of integrating redundant sources.

ATS or UPS? Or Both?

Does using an ATS mean you don’t need a battery backup system (a.k.a. Uninterruptible Power Supply)? No, the ATS and UPS have different jobs to do, and are used for different reasons. In fact, you may want to use both types of products at the same time.

A UPS is typically sized to provide power for a short period of time; typically, long enough to conduct a safe shutdown of the equipment depending on it. This may be a few minutes up to a few hours. In either case, a UPS does not provide redundant power. It provides an emergency dose of power for a short time. The difference between redundant and emergency power is important, and the needs of your equipment and environment must consider the benefits of providing each.

As stated, emergency power provides power for a short duration typically to ensure human safety, product safety, or even data safety. With a UPS, this emergency power would work even with the total loss of facility power, but not for long.

Redundant power through an ATS differs in that the intent is to guard against loss (or intentional shutdown) of a specific power source from within the facility. Using a second power source, power consumption may continue for extended periods of time. However, the ATS will not protect against a total loss of facility power.

These are two distinct power management needs, and each has a specialized piece of equipment to handle it. In some cases, you’ll want one or the other, or both.

An illustration depicting the arrangement of ATS to UPS to PDU products in a power system.
In many installations, the use of the ATS and the UPS will be used to support the PDU. The ATS combines redundant sources for long-term power options, and the UPS provides short-term emergency power in the event of the total loss of utility power.