Uninterruptible power supplies defeat unplanned downtime

How a UPS system enhances a generator’s system design

By Mark Nell December 15, 2022
Courtesy: AMETEK Powervar

Uninterruptible Power Supplies Insights

  • Times, loads and locations all can affect uninterruptible power supplies (UPS)
  • Modern UPS topologies are designed to offer a variety of power continuity and conditioning features suitable for different environments.

Nearly every industrial property shares a universal goal of maintaining business continuity and avoiding interruptions. This goal is especially important for manufacturing plants. Regardless of the industry, product or scale of operation, manufacturers are responsible for maintaining their mission-critical production, product output and high levels of quality assurance. For this reason, power outages are a serious concern, and most facilities have measures in place to account for them. Typically, these measures begin with a generator, or more likely a system of generators. Generator systems are an essential element of a well-designed plant. Their ability to provide power output to machinery in the event of an outage until a safe shutdown is possible is crucial to protect the quality of products in production and ensure peace of mind for plant managers.

There are many considerations that must guide generator system design: operating conditions, load characteristics and profile, transfer switches, and of course, adherence with up-to-date codes and regulations. Each of these factors regard how the generator system will operate and be maintained over time, but they fail to account for two key concerns. The first is the small yet crucial segment of time between power outage and generator system startup, and the second is the quality of power flowing from running generators to the connected electrical equipment.

Today’s uninterruptible power supplies feature low impedance isolation transformation technology and increased load inrush capacity.

Today’s uninterruptible power supplies feature low impedance isolation transformation technology and increased load inrush capacity. Courtesy: AMETEK Powervar

Modern uninterruptible power supply (UPS) topologies are designed to address these concerns effectively, offering a variety of power continuity and conditioning features suitable for different environments. While UPS design will vary based by brand, customizations and power environment demands, UPS devices come in distinct topologies, each working slightly differently to manage power input and protect connected devices:

  1. Battery backup uninterruptible power supplies remain on standby until a power outage event, transferring AC power from the power source to the connected device. In the event of an outage, the built-in DC battery assumes the role of the power supply and an inverter converts the DC power to AC to provide power to the connected devices.

  2. Line interactive: Line interactive UPS solutions, at least when paired with low-impedance isolation transformers, can adapt to variable incoming voltage, greatly reduce anomalies like noise and transients and also provide backup power like a battery backup UPS would.

  3. Online double conversion: Just about every UPS is technically a double conversion product, in that it converts the incoming AC power into DC, then converts it back to AC full-time, feeding tightly regulated power to the connected electronics. What makes online double conversion different is that it is running 100% of the time, which eliminates the risk of any electrical load loss, though the switching time for other products is less than a single cycle and is therefore negligible.

Time matters

The 20- to 30-second period between a power outage and a generator’s startup may seem fleeting, but it is important in a business sense. Especially in industrial applications, power outages can have significant detriments on equipment performance, including immediate equipment lockup. Furthermore, the problems aren’t always resolved automatically when the power is restored via the generators. What if equipment has a rebooting time whenever power is cut off? What if inclement weather is causing repeated blackouts? What if power goes out during the middle of an extended fabrication project that cannot afford interruption?

The half minute between power off and power on can grow problematic quickly and is a textbook example of unplanned downtime – the bane of business continuity and bottom lines. According to recent reporting from Deloitte, unplanned downtime costs industrial manufacturers as much as $50 billion each year. No plant manager should think they are immune to this issue, as 82% of companies experienced at least one unplanned downtime incident in the last three years.

All topologies of uninterruptible power supplies can solve this issue by ensuring the availability of AC output, keeping connected gear up and running when the power goes out. Once installed, UPS units are always on and ready at a moment’s notice to carry over until an alternative power source is engaged, safe shutdown is completed or a load shed is completed by safely powering down high-consumption components, preserving run time for the critical loads.

Load matters

Plant managers and engineers must understand the energy demands of their space when designing their generator system, specifically with regard to load profile and run time requirements. These concerns are affected by the presence of UPS systems. The transfer time and inversions associated with UPS technologies, along with additional products like electronic lighting ballasts, variable frequency drives, and general electronic equipment, can affect power draw and in turn cause a nonlinear electrical load.

Nonlinear loads can introduce harmonics into the electrical system that can require the derating of a generator system depending on total harmonic distortion. The dynamic consumption demands from nonlinear loads can impact the quality of power a generator produces, as engine speed, voltage, and frequency can experience temporary deviations from their steady-state conditions. These variations can impact equipment performance, so any generator systems that carry nonlinear loads should ensure that the connected uninterruptible power supplies are equipped with robust power conditioning features. The double online conversation UPS is an excellent candidate for nonlinear loads, as it provides both an uninterruptible power stream and a large spread of power quality assurance features to keep adjacent technologies running smoothly.

Location matters

Just as the location of a generator system has a substantial impact on its performance, so too does the location of a UPS. To deliver the best quality power during the short periods where all other power is out, UPSs should be near the equipment they drive. The power output from the UPSs will be clean, when clean power must travel long distances to reach connected equipment, the risk that the load will accumulate electrical noise increases. Modern, highly sensitive electrical components run at lower and more energy-efficient voltage amplitudes, which means even slight spikes and sags caused by noise have a larger proportional impact than they would on older, higher amplitude components. Without proper conditioning, these anomalies can manifest in the form of power interruptions, device lockups, and most painfully, degradation to the longevity of new systems.

Another reason to consider the location of UPSs in your generator system design is to facilitate the ease of installation and maintenance. Though actual dimensions vary based on unique need, some UPS units are as large as a common refrigerator, making them difficult to shoehorn without pre-planning. Integrators recommend setting aside 5 percent of square footage for power conditioning, with about a quarter of that share going to UPSs. The variety of topologies are available in different power configurations and sizes to lend themselves to space and functionality requirements.

Final words on uninterruptible power supplies

Failing to include UPS systems in a plant’s generator system design can uproot the operational integrity of your plant, leaving it vulnerable to inconsistencies of grid power and a range of anomalies associated with power supply interruptions. Equipment can lose power during the minute it takes your generators to start up, but it can also be left susceptible to dirty power once the generators are running. Knowing the grid is often unreliable, especially these days, the time to reassess your power plan and incorporate proper, intelligent UPS technology is now.

Author Bio: Mark Nell is a sales engineer with AMETEK Powervar.