Broadcast Electronics AM-2.5E, Руководство пользователя

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4-8
4-31.
POWER SUPPLY.
4-32. A single phase source of 196 to 252 volts ac 50/60 Hz is required to operate the
transmitter. The power source is routed through an RFI filter to prevent the coupling of
RFI components into or out-of the transmitter. A rear-door ac on/off switch provides ac
power control and disconnects all ac power to the transmitter when the door is opened.
The ac line is monitored for high/low conditions by an ac line voltage monitor. The
transmitter primary ac power will be interrupted if the ac line is above 260 volts or below
195 volts. Primary fuses protect the transmitter from over-current conditions. A power
factor corrector circuit modifies the ac line impedance to provide a power factor of
approximately 0.9.
4-33. The ac line voltage is sampled at the ac sample circuit board. The sample circuit board
provides an ac line voltage sample for application to the meter switch circuit board.
4-34.
POWER SUPPLY CIRCUIT BOARD.
DC operating potentials for the RF power modules
are provided by power supply circuit boards. One power supply circuit board provides dc
operating potentials for one power block. The AM-2.5E transmitter is equipped with 1
power supply circuit board. The AM-5E transmitter is equipped with 2 power supply
circuit boards.
4-35. The power supply circuit board consists of a: 1) switching power supply circuit,
2) conventional bridge rectifier circuit, 3) fault detection circuit. The switching power
supply circuit operates directly from the ac power source. No primary ac power
transformer is included in the circuit. An SCR controlled bridge rectifier circuit and a
switching regulator circuit converts ac potentials to dc potentials at a desired voltage.
Control of the dc output voltage is provided by a power control PWM signal from the
controller.
4-36. A transformer with five secondary windings provide low-voltage ac potentials to five
full-wave bridge rectifiers circuits. The circuits provide dc operating potentials for the
power supply circuit board and RF power module circuitry.
4-37. The power supply design provides the RF power modules with a constant and stable dc
operating supply by not responding to fluctuations or surges in the ac line voltage. The
supply will produce a constant dc voltage during high/low ac line voltage or surge
conditions.
4-38. The switching power supply output voltage is controlled by a power control PWM signal
from the controller circuit board. Current reduction at turn-on is controlled by a
soft-start circuit. The circuit is designed to generate start pulses synchronized to the ac
line phase to slowly bias the SCR bridge rectifier circuit on during initial turn-on
operations. The switching regulator circuitry is monitored for proper operation by an
overvoltage and loss-of-PWM signal circuitry. The switching regulator operation is
performed by IGBT (insulated-gate-bi-polar-transistors) transistors. The IGBTs are
designed to provide extremely reliable and efficient operation.