Specifications
The neutral of this WYE configuration is brought out to provide
60 VDC. L1 and C5 provide additional filtering for 150-180 Hz
ripple.
4.6.2.4 +230VDC Power Supply Crowbar Discharge Circuit
This circuit is comprised of four power MOSFETs operating in
parallel to discharge the +230VDC and +115VDC supply any-
time K1 and K2 are de-energized. Q1, Q2, Q3, and Q4 function
as switches which will be open when the supply is energized.
When K1 or K2 de-energize, a control voltage is applied to each
gate to activate the MOSFETs. This control voltage comes from
the 230VDC supply bus and is routed through R34 and “Nor-
mally Closed” auxiliary contacts on K1 and K2 to the individual
gate circuits. Therefore the discharge path is self contained, i.e.
no additional supply is needed to activate the circuit. R25, R26,
R27, and R28 are in series with each MOSFET for current
limiting. Each MOSFET has a zener diode across the gate to
source to limit the gate voltage to 10V. The 115VDC supply will
discharge through CR47 when the Crowbar activates.
4.6.2.5 +230VDC Supply Current Meter
The negative side of the A and B rectifier assemblies are tied
together on one end of the +230VDC power supply current
meter shunt SH1. The total +230 VDC supply current returns to
ground at this point.
Meter shunt SH1 is located in lower rear section of the right PA
compartment. The Supply Current meter (M2) is located on the
center PA compartment front door, and is connected across the
shunt.
The voltage across the shunt, which is proportional to supply
current, also goes to the supply current overload circuit on the
Analog Input board, through the switch board/meter panel. The
current overload circuit provides a remote supply current meter-
ing output as well.
4.6.2.6 Blower Supplies
The 13 blowers operate from 3 Phase 480VAC and obtain their
supply from F11, F12, and F13 which are connected to the
primary of A1T1A. Two of the three phases are directly con-
nected to each blower, while the third phase passes through
blower current monitors K6 through K9. K6 monitors the Left
Compartment, K7 the Center Compartment, K8 the Right Com-
partment, and K9 monitors both the Output Cabinet and the
Power Supply Cabinet. Normally when the transmitter is oper-
ating and the blowers are functioning properly, DS6, DS7, DS8,
and DS9 will be illuminated GREEN on the PowerSupply status
panel. Should a blower failure occur, the drop in blower current
will be sensed and the transmitter will foldback to a safe oper-
ating level. (See VIEW 1 for component locations).
12/16/03 888-2339-002 4-15
WARNING: Disconnect primary power prior to servicing.