Westinghouse SE 3718S, Manual

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2-4 D
ESCRIPTION
S
ECONDARY
S
WITCHING
P
OWER
S
UPPLY
The secondary switching power supply converts and distributes power from either the primary
switching power supply or the backup battery to all output terminals of the 3718S.
C
ONTROL AND
I
NDICATORS
C
IRCUITRY
The main function of the control and indicator circuitry is to sense and control the operation of
the rest of the power supply. Additionally, it reports on important power supply conditions either
by status indicators on the top panel or by sending signals directly to the ACU.
The conditions reported to the status indicators on the front panel include: The presence of AC
input power, whether a backup battery is connected, if that battery is fully charged, if ACU system
voltages are present and in range, and whether lock voltage is present and in range.
The conditions reported directly to the ACU include AC power failure (in case of short-term
outages) and impending battery failure (in case of long-term outages).
I
NDICATOR
LED
S
As shown in Figure 2-2, five LEDs are mounted on the SE 3718S control panel. These LEDs are
controlled by the control and indicator circuitry and function as follows:
AC ON Lights when unit connected to and operating from AC power
BATTERY CONNECTED Lights to indicate presence of battery.
BATTERY FULL Lights to indicate fully-charged battery. LED goes out when the
battery is no longer fully charged.
SYSTEM OK Lights indicating all system voltages are present and within limits.
LOCK OK Lights to indicate that lock voltage is available and within limits.
C
ONTROLS
CIRCUIT BREAKER Turns power supply on and off.
12/24 LOCK VOLTAGE Selects between 12V and 24V output at the lock terminals (J4)
GROUND ISOLATION Used to connect/disconnect low-voltage ground from chassis.
N
OTE
This feature does not disconnect the power supply chassis from third-wire grounding at the power
connector, but it does disconnect the low voltage common from the chassis ground and this can
be used to eliminate certain communications problems associated with ground loops.