Chapter 4 Theory of Operation
Revision W HF Series X-ray Generators - Service Manual
4-10 Quantum Medical Imaging
Three-Phase Line Monitor Circuit
When the Line Monitor circuit is configured for three-phase operation, a cir-
cuit is present on the Line Monitor circuit board that monitors all three phases
of incoming power to detect any phase(s) missing. If one or more phases are
missing, Phase A, Phase B or Phase C Optocoupler U4, U5 or U6 turns off
immediately for the time period when the phase is not present. As soon as
one of the optocouplers turns off, a signal is sent to the Logic Circuit to indi-
cate a fault condition, and prevents an exposure from being taken and stops
any exposure in progress. When the three phases are again present, the
Logic Circuit resets turns on Reset Transistor Q1, which returns the MISSING
PHASE output to an inactive level.
LINE MONITOR CIRCUIT (STORED ENERGY SYSTEMS)
The Line Monitor Circuit consists of four distinct circuits:
• The Battery Monitor Circuit
• The Storage Capacitor Discharge Circuit
• The Generator Auto Shutoff Circuit
• The Battery Charger Circuit
Their operation is as follows:
Battery Monitor Circuit
The Battery Monitor Circuit is composed of four independent voltage monitor
circuits that track the two positive (+) and two negative (-) battery arrays,
one each of which comprise the independent Anode Tray #1 (lower), and the
Cathode Tray #2 (upper) DC Battery Power Supplies.
The sum of each (+) and (-) pair produces a Voltage Sense (VSENSE) signal
proportional to the total output voltage present on each tray. The divider
ratio is 100:1. The V_SENSE ANODE (TP9) and V_SENSE CATHODE (TP10)
analogs are routed to Logic Board A1, which performs an A/D conversion, and
via software, monitors and determines if the battery power supply voltages
are within acceptable limits for proper system operation.
Additionally, a hardware Over-voltage Fault Detector protects the batteries by
forcing a charger shutdown if triggered.
Storage Capacitor Discharge Circuit
The Storage Capacitor Discharge Circuit exists to bleed-off the High Voltage
DC Charge on the Anode and Cathode Storage Capacitor Banks once the gen-
erator is turned off.
Upon turn-off, the generator’s internally switched +24VDC Low Volts Power
Supply collapses, allowing the normally closed contacts of Relays K7 and K8
to insert two 1.2 Kohm, 50-watt external bleeder resistors R1A and R1B in
parallel with the Anode and Cathode Storage Capacitor Banks. These resistors
discharge the capacitors to below 24 VDC within two minutes. When the
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