PMX MANUAL
4
118164-001 REV. A
1.1.2
Environment Requirements
Operating Environment
Operating Temperature
10 to 40
°
C (50 to 104
°
F).
Relative Humidity
20 to 85%, non-condensing.
Atmospheric pressure range
500 to 1060 hPa (375 to 795 mm Hg).
TRANSPORT AND STORAGE
Ambient temperature range
-40 to 85
°
C (-40 to 185
°
F).
Relative humidity
5 to 95%, non-condensing.
Atmospheric pressure range
500 to 1060 hPa (375 to 795 mm Hg).
1.2
THEORY OF OPERATION
1.2.1
Function Overview
The PMX X-Ray generator utilizes sophisticated
power conversion technology. A variety of
analog, digital and switching power conversion
techniques are used throughout.
The PMX generator is basically an AC to DC
power
converter.
Within
the generator,
conversions of AC to DC, then to high frequency
AC, then to high voltage DC take place. By
reviewing further the sub-assemblies, a basic
understanding of the process can be gained.
1.2.2
Line Rectification and Filtering
Basic AC line rectification provides the DC buss
voltage for the high voltage inverter, Anode
rotor drive, and the filament supply.
The input line voltage can vary from 180V up to
264V within the series.
The line voltage is connected directly to the EMI
filter. The EMI filter reduces conducted HF noise
on the AC mains. The output of the EMI filter is
connected to an off line auxiliary power inverter
circuit that provides 24V power for generating
other auxiliary supply DC voltages.
1.2.3
Inverter
The inverter is a “half-bridge” topology. Current
mode control is used for driving the inverter. An
IGBT power module employed. The IGBT
provides high frequency switching to control the
primary current flow to the high voltage
transformer.
Circuits on the Power PCB board provide the
gate control of the IGBT switches. The system
control board generates gate drive control
signals. The circuits on the Power PCB provide
the required gate voltages and offsets.
1.2.4
High Voltage Transformer
The output of the High Frequency Quasi-
resonant Inverter is connected to the primary of
the High Voltage Transformer. The High
Voltage Transformer is a step up type. Typical
secondary output voltage is in the range of
12.5kV depending upon output voltage ratings.
1.2.5
High Voltage Assembly
The High Voltage Assembly will vary depending
upon the model ordered. The circuitry typically
consists of an arrangement of half wave voltage
doubler.
A high bandwidth resistive/capacitive divider
provides voltage feedback for regulation and
monitoring. A sense resistor connected at the
low voltage end of the High Voltage Multiplier
circuit provides current feedback for regulation
and monitoring.
1.2.6
System Control PWB
Auxiliary DC voltages are generated in the low
voltage power supply section of the System
Control PWB.