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Section 2:
Introduction
Overall Operation
:
The EDP Double Conversion UPS series of power supplies provides filtered and regulated AC output power to operate
traffic signals, conflict monitors, camera equipment, lighting, and additional applications used in Departments of
Transportation and Intelligent Traffic Systems (DOT/ITS). These power supplies are designed to normally power an
intersection or highway system from the commercial AC utility line while maintaining an emergency battery in a state
of full charge. If the commercial AC line fails for any reason or if line voltage exceeds preset low or high limits, the
low voltage inverter within the power supply continues to provide power to the intersection or highway system load
while drawing its operating power from the battery string. After AC utility line power has been restored, the power
supply will revert to Double Conversion operation, supplying power to the intersection or highway system while
drawing operational power from the commercial AC utility line and simultaneously recharging the battery string. The
power supply will continue providing filtered and regulated AC power to the intersection or highway system load with
zero loss of output power during outages, brownouts, or spikes.
Primary Voltage
:
The EDP Double Conversion series of power supplies have been designed for operation from standard AC utility lines
with an overall voltage range of 55 to 155 volts for nominal 120VAC/60Hz models. UPS output frequency is matched
with the AC input frequency. The wide input voltage range is load dependant. Please see Specifications for output load
requirements regarding input voltage range.
Inverter Operation
:
The EDP Double Conversion UPS series provides uninterruptible power in the event of line voltage brownout, spike,
or failure. During these events, the inverter draws power from the battery string and provides regulated output voltage
to the load. The point at which the UPS switches to battery power is load dependant. A UPS with greater than 70%
load and line voltage less than 96V will switch to inverter operation after 1 minute during brownout conditions and
immediately switch to inverter during spikes and line failures. When input voltage returns within operating range, the
UPS will automatically return to Double Conversion operation. Please see Specifications for Acceptance and Detect
voltages.
Output Over-current Monitoring
:
The output of the EDP Double Conversion UPS series provides three preset current limiting functions that will
disconnect the inverter in the event of overload and short circuit of the output. Over-currents not exceeding 110% of
the model rated output current will provide 10 minutes of runtime until the inverter is disconnected. At 150% of
overload, the UPS will provide 10 second power intervals at which time the UPS will automatically attempt to
provide power to the load until the over-current condition is removed. This condition will test the overload every 45
seconds. Short circuit conditions rating at 200% of the model rated output current will disconnect the inverter within
50ms of detection until the short circuit is no longer detected. These features are self-correcting upon removal of
overload or short circuit.
Bypass Mode
:
In the event that the output is overloaded for an extended period of time while in Line Mode, the UPS will enter a
Bypass state. The inverter will be bypassed and the output powered directly from line voltage. This feature is self-
correcting upon removal of the overload and the inverter will begin to operate, providing filtered and regulated output
voltage.
