Nautel XL12, Technical Instructions

Page: 124 / 238

12 000 WATT AM BROADCAST TRANSMITTER
XL12
Page 6-11
01 January 2002
6.6.15.2 RF On Status :
The
RF On Status
output is applied to the remote interface PWB's
STATUS - RF ON
terminal. When the transmitter is
turned off, the
RF On Status
output is an open
collector. When the transmitter is turned on, but not
necessarily producing an RF output, the
RF On
Status
output is a current sink-to-ground.
6.6.15.3 Exciter B Status:
The
Exciter B
Status
output is applied to
STATUS - EXCTR B
terminal. When exciter A is selected, the
Exciter B
Status
output is an open collector. When exciter B
is selected, the
Exciter B Status
output is a current
sink-to-ground.
6.6.15.4 Power Level Status:
The
Power
Level Status
outputs are applied to the remote
interface PWB's
STATUS - PWR
terminals [
1
,
2
,
3
,
4
,
5
,
6
. When a power level is not selected, its
Power
Level Status
output is an open collector. When a
power level is selected, its
Power Level Status
out
put is a current sink-to-ground.
AC/DC POWER SUPPLY
6.7
The AC/DC power stage interfaces with the
three phase AC power source to provide all DC
power supply voltages for the host transmitter. The
AC/DC power supply is used to create the B+
supply which is applied to the RF power modules.
Supply vo48V, +24V, -24V, +8V and -8V
are developed for use by the exciter, control/monitor
and RF power stages. DC power supply control
PWB A28 and DC power supply monitor PWB A29
provide control and monitoring of all power supply
functions. Power supply status is applied to the
control/monitor function (see figure SD-6).
The Z1/Z2/Z3 secondary output of A23A1T1 is
applied through rectifier U1 to the DC power supply
PWB (A28) to create a +48V supply for the RF
drive stage's amplifiers. The Z1/Z2/Z3 secondary
output of A23A1T1 is also applied to the DC power
supply monitor PWB (A29) to monitor the status of
the AC supply.
AC line 1 and 2 inputs are applied to LVPS
transformer A23A2T1 which is used to create low
level AC supply voltages rectified in the DC power
supply.
EMERGENCY ON/OFF switch S1 is located on the front
door and is used to de-energize the charge and full
power relays and, therefore, the power transformer
A23A1T1 is removed. The transmitter will be
disabled until the
EMERGENCY ON/OFF
switch S1 is
pulled to its operate position.
6.7.1 MAIN POWER TRANSFORMER:
The
main power transformer (A23A1T1) is a three phase
distribution style transformer. The primary windings
are a Delta configuration which should be connected
to a Wye configuration AC power source at the
transmitter site. The transformer secondaries
X1/X2/X3 and Y1/Y2/Y3 are zig-zag,
wye
configuration producing nominally 233 vrms line-to-
line.
6.7.2 B+ POWER SUPPLY/DISTRIBUTION:
The AC source voltage is applied to power
transformer A23A1T1 thru full power contactor
A23K2, charge power contactor A23K1 and
charging resistors R1 thru R3. When AC is first
applied to the transmitter from external AC breaker
box, contactor A23K1 is energized by the power
supply PWB. The 3-phase AC supply voltage is
applied thru A23K1 and charging resistors R1 thru
R3 to A23A1T1. The wye/delta secondary outputs
of A23A1T1 are applied to rectifier assemblies A25
and A26. The
B+
outputs of the rectifier assemblies
are applied thru chokes A23L1 and A23L2 to charge
the reservoir capacitors in the RF power stage.
When the B+ supply has charged to a sufficient
level, as seen by the B+ sample at the
B+ monitor
input (E24) of the power supply control PWB,
contactor A23K2 is energized. Contactor A23K2
shorts out charge resistors R1 thru R3 and applies
the 3-phase AC supply voltage directly to
transformer A23A1T1. A
charge completed
signal
is applied to the control/monitor function indicating
the capacitors have charged and the full power relay
is energized. The temperature of the charge and
discharge resistors is monitored by
temp sense p/s
thermistors RT1 and RT2 and applied to the DC
power supply PWB. The duration of the charge and
discharge cycles is monitored by the power supply
monitor PWB (A30). The output of DC current
shunt R4 (+)/(-) is applied to the control/monitor
function for a DC current indication on a transmitter
front panel meter.