Section 9 1MAC309294-MB F
Other functions
428 RER620
Technical Manual
If one desires to switch off the system while operating on battery power (before the battery
discharges to 40 Vdc), open the battery fuse block.
9.1.3.3 Auxiliary Power Supply
The UPS has an isolated 30 watt output Auxiliary Power Supply (APS) for auxiliary
equipment such as radios, modems, etc. The APS has two output voltage settings, 12 Vdc
and 24 Vdc. The voltage selection is made by communications from the RER620. The
supply may be switched on or off by communications as well. In applications where the
supply is not needed, switching it off will extend the battery life. Once set, the APS will
remember its settings after a UPS system reset. If the supply has never been setup, its
default value is 12 Vdc and switched off. The recommended maximum steady load for the
APS is 24 watts.
The APS is not fused, but it is protected with protection firmware and hardware that will
allow for load power to exceed 24 watts for only limited periods of time. The firmware
protection is based on two I2T (Current squared * Time) curves, one fast and one slow.
The slow curve will go into pickup at 24 watts and, if just over pickup, will timeout in
about 3 minutes. The fast curve will go into pickup at 28 watts and, if just over pickup, will
timeout in about 15 seconds. If the APS shuts down due to a timeout on the fast or slow
curve, then there is a three minute cool down time. At the expiration of the cool down timer
the supply is switched back on and the RER620 is notified. The hardware instantaneous
protection circuit will shutdown the APS at about 38 watts and will retry to start the supply
about once a second.
9.1.3.4 Actuator Drive Power Source (Boost Supply)
The UPS has a programmable power supply that has a range from 60 Vdc to 250 Vdc. The
output from this supply provides the power to operate the actuators for the recloser.
Usually the voltage selection is made once through communication from the RER620 and
left at that setting for the life of the UPS unit. The default voltage is 240 Vdc. The wattage
for this power supply may peak as high as 80 watts during fast reclose operations when
multiple pole operations are required in quick succession. The power source for this supply
is the 60 Vdc rail within the UPS. The voltage from the 60 Vdc rail is increased by means
of an inductor, diode, and FET arrangement common in flyback type boost circuits.
This supply has sufficient wattage to harm itself if driving a low impedance load. To help
prevent this, there is a 300 ohm resistor used in series with the 60 Vdc rail used to charge
the supply’s load. If the load can not be charged to about 40 Vdc through the 300 ohm
resistor, then the relay contacts (RA1) that bypass this resistor will not engage. The boost
will not operate until RA1 has closed.
9.1.3.5 Heater control switch
The heater relay (RA3) is used to control the low-voltage-cabinet heater. The UPS makes
use of its integrated temperature sensor to determine when the heater should engage. The
UPS can also select to switch off the heater in the event there is no or limited input power.
The output from this supply will remain charged for many hours after the
UPS has been powered down if not discharged with an external load.
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