©
Panduit Corp. 201
4
OPERATION MANUAL
UPS003024024015
Page: 8 of 29
1. INTRODUCTION
BACKGROUND
1.1.
The UPS Uninterruptible Power Supply (UPS) is designed to provide backup power to a DC
load in the event of a power outage. The unit utilizes Electrochemical Double-Layer Capacitors
(EDLCs), as the energy storage device to provide a long operating life without the need for
battery replacement. The UPS accepts a 24 to 28VDC input voltage and provides a 21 to
28VDC output voltage to a load with a maximum output power of 35W. The bank of twelve
350F EDLCs provide energy storage of approximately 15kJ which can
supply a 35W load for a
minimum run time of 5 minutes. The UPS can be used in a redundant power supply system
and as such, it can monitor the power delivered by a second supply to the load through an
external sense resistor. Operating status and control is provided via a web server running on
the UPS that may be accessed via a web browser running on a PC connected to the same
network as the UPS. The ON/OFF switch may be used to turn the UPS off which removes
voltage from the terminals so that the unit is safe for installation or transportation.
The UPS utilizes multiple EDLC cells in series and the charge voltage is applied across all
cells in the series or the
“
stack
”
of cells. Due to small differences in cell capacitance and
leakage current, it is possible for one cell to charge to a slightly higher voltage than other cells
in the series stack. As the cells are run very close to their maximum operating voltage, it is
necessary to monitor each of the twelve cells and adjust the individual cell voltages to ensure
that they do not exceed their maximum voltage rating. The UPS includes a microcontroller
that performs this
“
cell balancing
”
function by monitoring each of the twelve cell voltages and
connecting a
“
bleed resistor
”
across the cell if the voltage across any one cell gets too high.
This process is also used to increase the voltage of any cell that has a very low cell voltage in
order to ensure that the average cell voltage is not any higher than necessary. The UPS also
uses the cell balancing circuitry to measure the capacitance and equivalent series resistance
(ESR) of each cell. This information can be used to calculate the energy storage capability of
the UPS as well as to project the operating lifetime of the unit.
Figure 1 shows a photo of the UPS system excluding the optional load sense module.
Figure 1: UPS
PURPOSE
1.2.
The purpose of this document is to provide the user with the information necessary to
operate the UPS.
