When power goes out, a ups power supply will let you keep working. As weather extremes and storms increase, power outages are likely to continue to rise.

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 UPS Uninterruptible Power Supply system to keep your business and other sensitive equipment running smoothly.

In this article we’ll explain how a ups power supply 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 power supply works with generator

ups power supply works with a backup 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.

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 power supply 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.

UPS power supply installation case

Matching a Generator to your UPS power supply

If the mains power fails, your UPS will accept the load and support the critical systems that can’t withstand a short break in power. The UPS then acts as a power bridge, keeping critical systems operational until the generator supply is established and synchronises with the UPS, before picking up the load.

A Generator must be sized adequately for the UPS power supply it is supplying. As well as being capable of handling the step load of the UPS, the Generator must have sufficient capacity to recharge the UPS Batteries and cover the conversion losses of the UPS. The maximum step load of most generators is around 65% of the total rated capacity of the generator.

Sizing a diesel generator and UPS system

Maybe you need to size a diesel generating set for a UPS. Sizing a diesel generator for a UPS as follows:

KVA gen = KVA UPS + KVA battery charge divided by 0.8 x ∩ UPS

Where: ∩ is the efficiency of the UPS 0.8 is the deration factor

UPS manufacturers lay down frequency parameters that require diesel generators to feature an electronic governor. This part is sometimes referred to as a speed controller. While older generator sets employ mechanical or electrical controls, electronic controls power newer generator sets. By fitting a diesel generator with an electronic governor, frequency is maintained within minus or plus 1%.

Choosing a UPS system for your generator

  1. Double conversion ups
Double conversion online ups topology

A UPS power supply 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

pure sine wave online ups

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.

Calculate ups capacity

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)

Avoid a problem with overheating

Temperature also plays a major role in backup. For example, when a generator runs, a rise of 10 degrees Celsius is typical. If the ambient temperature is around 40 degrees Celsius, the added heat can damage the generator and many generators will need to be derated to operate above this. Larger generators with sufficient electrical capacity typically operate at higher temperatures by oversizing them. Therefore, heat becomes less problematic.

When choosing your UPS and generator size, you also need to provision and scale your generator for more power. Oversize the generator between 1.25 and two times the UPS output when the generator only supports the UPS. Increase this amount to the required rating when the generator needs to support extra electrical equipment, such as air conditioning, emergency lighting, or lifts.

When deciding on UPS systems and generators, you need to identify the various levels of power protection needed for different pieces of equipment as well as calculate the power loading for the generator you select. Choose the generators should meet the requirements for surge current, UPS power, harmonics, operational temperature, synchronisation, and future electrical loads. Typically, the generator size should not surpass the UPS power rating by around 1.25 to 3.00 overall.

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