Technical Manual C-Band 1 MW Transmitter Pulse Systems Part Number TR-1038 Magnetron SFD 313A August 22, 2003 Prepared By: Pulse Systems Inc.
TABLE OF CONTENTS GENERAL DESCRIPTION ..................................................................... 2 Introduction .................................................................................. 2 System Specifications .................................................................... 2 General Technical Discussion .......................................................... 2 Mechanical ................................................................................... 4 POWER SUPPLY SECTION ...
GENERAL DESCRIPTION Introduction The system described in this manual consists of four main parts: A: B. C. D. The Main High Voltage Power Supply The Modulator System The Corner Cutter Filament Power Supply In order to achieve the design objectives of this contract, our design approach has to follow state-of-the-art technology in solid-state design.
F. G. Hard Tube Modulator Control Solid-State Filament Power Supply The Modulator section contains the following sections: A. B. C. D. Switch Driver Assy PRF Driver High Power Switch Section Magnetron Peak Current Detector The input voltage for the system is 220 VAC single phase and it enters the system via a connector located in the rear lower panel of the cabinet. The input line voltage enters the system via a circuit breaker located on the control panel.
in the power supply. The function of the modulator is to receive the input signal and provide a high-power pulse of 36-38 KV at the cathode of the magnetron, thus causing the magnetron to oscillate at C-Band frequency under the selected pulse width set by the modulator control circuit. The maximum cathode peak current under the above conditions is 60 Amperes peak. The above voltage and current levels result in a peak output power of 1.0 MW.
The modulator on the other hand is contained in an oil-filled container for insulating and cooling reasons. The modulator is mounted above the power supply on its own compartment. Next to the modulator, the corner cutter assembly is mounted and its output is connected to the cathode terminal of the modulator. The magnetron is mounted above the modulator shelf and the high voltage bushing projects into the modulator compartment through a hole located on the magnetron shelf.
POWER SUPPLY SECTION Technical Approach In order to meet our design objectives of reliability, efficiency, simplicity and cost, our approach for the system is derived from our past experience. For the power supply, we feel that the series resonance converter topology is the best choice. First the efficiency of the system is greatly optimized under this topology and both the RFI and EMI levels are kept at a minimum.
D: -12 VDC The above voltage levels are regulated via linear series regulator circuits with associated filter networks. The input line voltage enters next the Power Factor Correction Circuit. The power factor modules (three) rectify the input line voltage, regulate it, and limit the input inrush current to a reasonable level.
Metering circuits are provided for the output voltage of the power supply, the output current, the filament voltage, the magnetron average current and the system voltage. The return section of the power supply goes through a sensing resistor whose level is detected and processed for over-current protection. Mechanical Considerations Figure 1.0 shows the mechanical configuration of the power supply.
MODULATOR SECTION Technical Approach Several solid-state modulator systems have been designed, built, and delivered by Pulse Systems. All designs feature the Mosfet or IGBT technology. Our design approach for reliable operation has been to limit the switching voltage level within the solid-state switch capability and to avoid stacking switches in series configuration. The design approach is shown in Figure 6.0 Schematic diagram For the discussion, which follows, we make reference to Figure 6.
The schematic diagram of the corner cutter is shown in figure 6 next to the modulator circuit diagram. The solid state switch assembly is turned on during the positive portion of the drive pulse and kept off when the drive pulse goes to a negative bias level. The output pulse-width of the system bears a close relationship to the drive pulse of the switch driver.
section of the power supply and provide high voltage to the four modulator channels. Terminals E4 and E5 are connected to the primary winding of the heater power supply inverter transformer. There is a BNC connector located along the same line with the above terminals dedicated for the input drive pulses from the modulator control circuit. All the terminals located above the BNC connector are the control and feedback voltages to and from the modulator.
MAGNETRON HEATER POWER SUPPLY Technical Discussion The magnetron heater power supply consists off three parts: A. B. C. Heater meter control card High voltage inverter transformer Filter section The control card for the heater power supply is shown in figure 8.0. The control circuit generates a PWM signal to drive a discontinuous mode power supply. The high voltage section of the power supply is inside the modulator including the filter section and feedback.
OPERATING INSTRUCTIONS Procedure For Setting All System Parameters After the system has been received and inspected a cable should be prepared for the outside power connection to the 220 VAC 50/60 Hz. The external source should be capable of providing 220 VAC 50/60 Hz at a minimum current of 25 amps. Before we apply power to the system, we make sure that the high voltage adjust potentiometer is set all the way counter clockwise.
important things to remember are the 60 Amperes of peak cathode current and the 0.001 duty cycle. The peak cathode current is easily observed on the screen of the oscilloscope. In the case of the duty cycle, each pulse condition has to be evaluated to ensure compliance with the magnetron specification.
MAINTENANCE Introduction This sections covers information regarding the maintenance of the system. In general, the incorporation of solid-state devices makes the system an easier system to care for as time goes on. There is basically no component in the system that has a time limit or exhibits performance degradation as a function of time. The Power Supply Section The power supply section is cooled by forced air-cooling fans located in the rear section.
