1.0 Introduction
The Lite-Minder Central Inverter System integrates the latest inverter and microprocessor
technology to produce a Pure Sine wave power output intended for use in Emergency Lighting.
The Lite-Minder is very efficient. It typically has a steady state loss of just 2 percent of full load
while online which makes it ideal for energy saving and green initiatives. It is designed
specifically for emergency lighting from the ground up and meets the needs of all lighting loads
since it is a pure sine wave output. Lite-Minder was designed and developed by an Emergency
Lighting Manufacturer and is a culmination of market requirements that require high efficiency,
load compatibility, energy savings, low cost, and high quality.
Lite-Minder produces a Pure Sine wave and this is the ONLY method of power that will ensure
any lighting load will be powered safely, efficiently and effectively.
1.1 Mechanical Design Features
Batteries and electronics are contained in a single cabinet which makes installation very easy.
Mounting can be achieved on a wall or floor and there are electrical knock outs (EKO’s)
available on all surfaces. Quick access to the interior of the cabinet for battery inspection and
maintenance is accomplished by the removal of two screws which holds the front shroud.
Single module containing all electronics can be easily removed for upgrade or replacement.
This module concept makes maintenance and repair easier and more cost effective because
specialized training and knowledge in a Central Inverter System is not required.
1.2 Electrical Design Features
Through the use of Pulse Width Modulation (PWM) and the latest MOSFET technology, Lite-
Minder can produce a Pure Sine wave output which is compatible with all types of lighting
loads. A high crest factor of 4 is extremely beneficial for high inrush loads and also ideal for
bringing Normally Off lighting loads on from a cold start. The high crest factor also improves
the dynamic response so mixing Normally on and Normally Off loads together causes less
performance loss than traditional inverters. Since the active PWM regulation scheme produces
a very low THD waveform, the Lite-Minder can power up even the most demanding loads with
power factor capabilities ranging from 0.5 leading to 0.5 lagging.
There are three distinct outputs from the Lite-Minder which are Normally On, Normally Off and
the Switched Outputs. The Normally On Output is always present under normal utility power or
emergency power. The Normally Off Output is only present under emergency power so it is a
switched output when the Lite-Minder runs under emergency power.
The Switched Output is a user enabled output capable of switching Emergency Lighting loads
on and off making energy savings and green initiatives easy to accomplish. The switched
output is enabled by a switched command input signal of 120-277 VAC. Any output including
Normally On, Normally Off or the Switched Output is capable of producing full output power
and has no de-rating which means that 100 percent of the units rating can be driven from any
output. The switched output is also tied to the VTD function for HID applications having
Normally Off light sources. The batteries are charged by a temperature compensated charger
integrated into a bi-directional converter. A three rate charging scheme and bi-directional
converter topology ensures maximum float life and minimal ripple current on the batteries.
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