Emergency Lighting Inverters: The Basics

In the critical power equipment industry we get a lot of questions regarding emergency lighting. This article is the first in a three part series discussing what a lighting inverter is, how to maintain it, and what standards exist that facilities need to adhere to. Before we can discuss emergency lighting inverter maintenance and standards, it’s important to understand the different types of lighting inverters, what they do and why they are important.

What is a Lighting Inverter?

A lighting inverter converts DC battery power to standard AC voltages to provide back-up for lighting systems in the event of an emergency. Some inverters also provide continuous, filtered power for many styles of lighting and is often referred to as a “UPS (Uninterruptible Power Supply) for emergency lighting”.  Emergency lighting inverters are designed to be used in many applications that can also go beyond emergency lighting applications. Fire alarms systems, emergency lighting, exit lighting, lighting control systems and other critical or life safety related equipment are often supported by an emergency lighting inverter.

Lighting inverters differ in transfer time, voltage regulation, and power conditioning. The standards for emergency lighting inverters are defined in the UL924 test procedures. UL924 is UL’s standard for Safety of Emergency Lighting and Power Equipment. Some inverters may have a short delay, typically measured in milliseconds (ms) to respond to a power outage, while others provide a seamless transfer or are online double-conversion systems. The seamless transfer systems provide the kind of power necessary for HID, lighting control, and many alarm circuits.

Transfer time is the time it takes to recognize and deliver emergency power. Zero transfer time ensures that there is no interruption of power; a very important factor with HID lighting systems such as high pressure sodium lighting. Lighting control systems and alarm circuits can also be powered by a no-break transfer or double conversion inverter.

Tip: Make sure to take note what tolerance each piece of your critical power infrastructure requires to avoid unnecessary problems down the road.

Voltage regulation ensures that voltage drops and brownouts do not affect the overall lighting system. Voltage regulation also ensures proper lighting levels during normal operating conditions in “Normally On” circuits. Power conditioning prevents surges and transients from reaching the electronic ballasts, thus providing longer life of the lighting fixture or other protected asset.

Types of Lighting Inverters

There are two different installation approaches when it comes to lighting inverters: central lighting and dispersed lighting. A central lighting inverter provides a centralized solution to emergency lighting and power back-up with a wide array of options designed to minimize maintenance requirements and optimize emergency lighting performance.  A central lighting inverter can power the same indoor or outdoor fixtures already in place for task and convenience lighting when some or all of those fixtures are designated as “emergency lighting fixtures.” Dispersed lighting is where each individual light is powered by its own battery.

Central lighting has a higher capital investment, but a lower cost in operational maintenance expense. Central lighting is also easier to maintain as there is one central location and one battery system that needs to be tested and discharged to meet code requirements.

Dispersed lighting is lower in cost initially, but can have hidden, higher total cost of ownership. Dispersed lighting is also more cumbersome to take care of as you have to go to each and every single light to test batteries and functionality.

Emergency lighting inverter systems are essential to maintaining power and light during downtime. It’s important to understand the different types of lighting inverters and how they function. Stay tuned for our next article in the series which will go into detail on how to maintain your lighting inverter.

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  1. […] inverters are typically used for life safety applications and usually have a longer run time requirement than a UPS system.  In fact, the UL minimum standard […]

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