Selecting Load Banks: A Guide to Load Bank Types

Load banks are used to test backup power sources such as generators, batteries and uninterruptible power supplies (UPS) to ensure they will function as intended during a power outage. They work by generating all or most of the operational load of the power source, applying it to the power source and then dissipating it safely. But what are the various types of load banks, and what criteria should you use when selecting load banks?

The four main types of load banks, described below, are designed for particular applications. Understanding how they differ and their ideal uses will help you choose the right one. Most come in both compact, portable models and large, stationary models suitable for commercial and industrial settings.

Resistive load banks

Resistive load banks, the most common type of load bank, allow you to test a power source at 100% of its capacity by simulating resistive load scenarios. They mimic a load by converting electrical energy into heat that is dissipated through convection.

When to use resistive load banks

Resistive load banks work well for testing small generators, portable generators, incandescent lights, air conditioning and heating systems, large chiller systems and UPS systems. Portable models are ideal for networked generator banks such as you might find in a data center.

Most resistive load banks are designed for alternating current (AC) power sources, but direct current (DC) models are also available to test batteries and other DC power sources used by many small devices, home appliances, computers and electric generators.

Resistive load banks don’t test specific components for future problems that could cause a complete system failure so they should not be used for emergency applications.

Reactive load banks

Reactive load banks simulate real-world operational loads to test power source at its rated power factor. They convert electrical energy into a magnetic field using inductive (lagging power factor) loads or capacitive (leading power factor) loads, depending on the application. They can also test alternator function, kVAR load sharing and response to sudden changes in load demand. Some models can add capacitance to improve power factor and regulate voltage.

Reactive load banks allow you to test power sources for sensitivity to voltage dips by creating a lagging power factor of 0.8 with a 75% load.

These load banks can be more expensive and more complicated to use than resistive load banks. Additionally, they can cause voltage drops that could negatively impact system performance.

When to use reactive load banks

Reactive load banks are ideal for testing equipment powered by electric power sources such as computer servers, UPS systems, motor-driven equipment, capacitors and transformers. They are often used during facility commissioning. Capacitive load banks can also be used to correct power factor at facilities with low-power factors or to increase the voltage on utility power systems.

Resistive-reactive load banks

Resistive-reactive load banks combine the capabilities of both types of load banks to ensure your backup power system will work in an emergency. They allow you to test your power source at full capacity and under real operational conditions. They are ideal for recreating multipurpose conditions such as the combined loads of heaters, lights and motors. They can predict the failure of individual components in a system.

When to use resistive-reactive load banks

These load banks are often used in large facilities, such as data centers, where multiple generators run in parallel configurations. In that scenario, the load bank tests the ability of a generator to withstand sudden load changes when one unit fails. They are also used to test switch gears, turbines, generators, UPS systems, solar inverters and substation protection systems.

Generally speaking, a resistive-reactive load bank provides more system protection than resistive or reactive load banks.

Electronic load banks

Electronic load banks are programmable units that use automation for testing and troubleshooting electrical and electronic equipment. They can detect sudden power spikes and stabilize the load to protect against damage. They can also test average and peak load capacities.

When to use electronic load banks

Because of their ability to precisely monitor and test, electronic load banks are favored by hospitals and the airline industry as well as transportation, telecommunications and mining companies. Be aware that precision comes at a price: Electronic load banks are typically more expensive than other types.

A reliable backup power supply that protects against system failures and resulting financial losses during power outages should never be taken for granted. Load bank testing gives you peace of mind by validating the performance of your emergency power sources. To better understand the different types of load banks and which one is best for your application, contact the power and HVAC experts at United Rentals.

Visit our online marketplace to browse our full line of load banks.