How a UPS System Works with a Backup Generator

As weather extremes and storms increase, power outages are likely to continue to rise. According to the U.S. Energy Information Administration, U.S. customers experienced an average of nearly six hours of power interruptions in 2018.

If you have invested in a generator, you’ve prepared for when a storm hits, right? Almost. Even with a generator, you still need a battery backup, also known as an Uninterruptible Power Supply (UPS) system to keep your business and other sensitive equipment running smoothly.

In this article we’ll explain how a UPS works with a generator and then outline the benefits of utilizing a battery backup in this way. Finally, we’ll provide a few tips on and how to find the right battery backup for your generator.

How a UPS works with a generator

Generators generally support mission critical power needs such as heating, AC, IT, electronics, etc., which creates continuous changes in power requirements. The frequently changing load requirements makes it difficult for the generator to maintain a consistent frequency output. These variations can trigger some UPS systems to switch on and deplete UPS battery power.

A UPS system can regulate this power and specifically, Online Double-conversion UPS systems are designed to accept variations in frequency as part of their normal, everyday operation, preserving battery life. An online UPS system continually converts incoming AC power – whether from the main power supply or a generator – into DC power, and then reconverts it back into stable AC power with a sine wave. That’s the power wave form sensitive computers and other equipment demand.

The benefits of using a UPS system with a generator

There are many advantages to using a UPS system with your generator. First, a UPS system bridges the power gap when a generator starts up. When a power outage occurs, a generator doesn’t turn on instantly. In fact, it can take a generator up to a minute to start producing power. During the gap of time it takes for the generator to start working, the UPS system will instantly switch to battery backup power so none of the connected devices will feel the effect of the power outage. For sensitive office equipment, having a UPS system to bridge the gap will ensure your devices, your work, and your productivity stay connected and protected.

Second, a UPS system cleans the incoming power. A generator can produce inconsistencies and fluctuations in voltage and frequency ranges. An online UPS system takes unstable generator power and delivers consistent and clean output ensuring your sensitive equipment continues to function correctly.

Considerations for choosing a UPS system for your generator

1. Power conversion

A UPS system with online double-conversion topology (and generator mode) will constantly filter dirty power and produce clean AC output power. Dirty power is noisy, which produces a jagged sine wave but prevents maximum power output. Dirty power also requires your devices to work harder to function, which may shorten their usable life. In contrast, clean power produces a smooth sine wave and allows for maximum power output.

2. Frequency tolerance

A UPS system is equipped to handle the wide frequency range produced by your generator. Standby and line-interactive UPS systems are typically more sensitive and will switch to battery power more often. In contrast, an online double-conversion topology UPS system will limit the need to go to battery backup power and ensure seamless operation of your connected equipment.

3. Capacity
The UPS system must have the capacity to support the power load of the connected devices plugged into it. Additionally, the continuous generator capacity rating must be at least twice the rated capacity of the UPS system.

The load wattage should not exceed 80% of the capacity of the UPS system. To calculate the minimum capacity needed for the UPS system for the IT server rack in the example above:

1100 (Load) x 1.25 = 1375 (Minimum UPS Capacity)

These days, generators are vital, especially in areas most affected by inclement weather. You can protect your equipment and your productivity by ensuring seamless operation during a power outage by complementing your generator with an online double-conversion topology UPS system.

CyberPower Smart App Online Series UPS systems include a Generator Mode setting specifically designed to work with generators. For more information, visit our online resources:

Smart App Online UPS Systems
UPS System Selector
Choosing a UPS system
Power Assessment