January 25, 2017 at 3:18 pm #1180
Ch. Zeshan YousafParticipant
The transmitter circuitry is subdivided into five basic stages.
• Ac-Dc power stage
• Exciter stage –
• Control/monitor –
• RF power stage –
• RF output network – (includes combiner and filter)
1- Ac-dc power stage
The ac/dc power supply stage contains the input power transformer that receives the main ac input to the transmitter. It also contains the transmitter’s low voltage power supplies and rack interface PWB. The ac/dc power supply stage also include a three-phase SCR rectifier assembly, Hall Effect current sensor, and B+ distribution assemblies. With the exception of the power transformer, which has its own cabinet, each cabinet in the transmitter system contains its own ac/dc power stage components.
The secondary of the power transformer is applied to the SCR rectifier assembly to create the transmitter’s B+ voltage. The output of the rectifier assembly is fed through the Hall Effect current sensor, which supplies a dc current signal to the rack interface PWB. The rectifier assembly output is applied to the B+ distribution assemblies, which then provide the B+ voltage to the RF power modules, and a B+ sample to the rack interface PWB.
One phase of the power transformer’s secondary is also used to provide a source for the low voltage dc power supplies and an ac sample for the rack interface PWB. The low voltage power supply outputs (+48V, +15 V and +12 V) are distributed throughout the transmitter via the rack interface PWB.