Nautel NV7.5, Operation And Maintenance Manual

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NV10/NV7.5 Operations and Maintenance Manual Description
Page 1-2 Issue 3.4 2016-08-03
Ac-dc power stage
See electrical schematics
SD-1
(
A
,
B
or
C
),
SD-2
and
SD-3
.
The ac-dc power stage converts the ac power source to a positive dc voltage (PA volts) for the
transmitter's intermediate (IPA) and RF power amplifiers. The transmitter accepts a wide
range of ac input voltage options:
– 3-phase, 180 - 264 V ac (208 V ac nominal)
– 3-phase, 312 - 457 V ac (380 V ac nominal)
– 1-phase, 180 - 264 V ac (240 V ac nominal)
The ac-dc power stage provides power to operate cooling fans in the power supply modules,
RF power modules and reject load modules. It also provides power to the low voltage power
supplies, which generate the low level dc voltages (±15 V and +5 V) used throughout the
transmitter, and to the +12 V dc power supplies for the SBC (single-board computer) and AUI
(advanced user interface).
The ac-dc power stage comprises ac input terminal blocks TB1, TB2 and TB3, an ac
distribution assembly (A6), a power supply distribution PWB (A7), SBC/AUI power supplies
A (U1) and B (U2), LVPS modules A (U3) and B (U4), fan power supply modules A (U7) and B
(U8), IPA power supply modules A (U9) B (U10), and dual PA power supply modules (U12
through U19) for each of the four RF power modules. There is also a PS interface PWB
associated with each power supply module (fan, IPA and PA).
Power supply modules
See Figure
SD-2
. Power supply modules U9 through U19 convert the ac input voltage to a
regulated dc supply (IPA volts and PA volts) for all four RF power modules (module contains
both IPA and PA). Each switching power supply module provides 2000 W output, at typical
levels of 50 V and 40 A. The modules regulate the output voltage based on a PA (or IPA ) Volts
Control input from the control/monitor stage. Test points on the associated PS interface PWB
allow monitoring of module presence and ac input status. Each module has a built-in cooling
fan and each senses out-of-regulation and excessive temperature conditions and applies PS Fail
and PS Temp alarm signals to the associated RF power module. Both conditions cause the
power supply to shut itself down, thus reducing the transmitter's RF output.
The same modules are used for fan power supply modules U7 and U8. Their PS Fail and PS
Temp alarm signals, as well as the PS Module Present status signal, are applied to the control/
monitor stage.