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EMERGENCY
POWER OFF (EPO) OPTION FOR GALAXY SERIES UPS SYSTEMS
INTRODUCTION
This application
note will describe the EPO (Emergency Power Off)
option, which is available for Nova’s Galaxy
Series UPS systems.
DESCRIPTION
The EPO
option is intended to allow the user to have a
method of immediately turning off all output power
from the UPS. The normal method of power off is
for the user to “hit’ his EPO for the
room or facility. This would remove all power
from the room and the equipment would normally
stop operating. Due to the presence of the UPS
battery, the UPS will see the removal of input
power as a power failure and it would continue
full, uninterrupted operation of the battery.
In order
to allow the UPS to differentiate between a power
failure and an EPO event, the UPS is outfitted
with a special circuit breaker in the battery
circuit. When the customer’s EPO circuit
is activated, the EPO signal is used to also trip
the battery circuit breaker associated with the
UPS.
There are
several ways in which the battery circuit breaker
may be tripped. Some applications work by the
momentary or temporary application of voltage
to the trip coil of the battery circuit breaker.
This voltage may be low or high, and may be AC
or DC. It is important to specify these details
when working with a Nova applications engineer
as the UPS specifications are being determined.
The most popular choice of circuit breaker trip
coil is customer-supplied 24 VDC.
Alternative
choices of circuit breaker trip voltages include
the actual battery voltage. In that case, we momentarily
pass the battery voltage through the trip coil
of the circuit breaker. The circuit is completed
through the customer’s EPO button. The circuit
is not isolated and must not be grounded. Additional
choices of circuit breaker trip are available
upon request.
Some applications
require the EPO function to also trip the AC input
to the UPS. While this is not normally the case,
Nova can accommodate these special applications.
Please
consult with an applications engineer at Nova
for assistance with the EPO option by clicking
here howard@theallpower.com
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