Quantum ODYSSEY HF Series, Service Manual

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Chapter 4 Theory of Operation
HF Series X-ray Generators - Service Manual Revision W
Quantum Medical Imaging
4-9
two identical voltage-monitoring circuits (anode and cathode capacitor banks)
for three-phase systems.
On three-phase systems, each circuit produces a VSENSE voltage that is pro-
portional to the voltage of the anode or cathode capacitor bank. (The ratio of
the voltage across either capacitor bank to the voltage at the output of the
line monitor circuit is 100:1). The VSENSE (ANODE) and VSENSE (CATHODE)
voltages are sent to the Logic Circuit to determine if the line voltage is within
acceptable limits for proper system operation. On single-phase systems,
there is one capacitor bank each for the anode and cathode. In this case, the
capacitor bank is connected to the anode circuit only (JP1-2 is connected to
JP1-3) on the Line Monitor circuit board. The result will be that the micropro-
cessor will read the same capacitor bank voltage at VSENSE (ANODE) and
VSENSE (CATHODE).
Capacitor Discharge Circuit
The Capacitor Discharge Circuit connects bleeder resistors across the storage
capacitor banks to discharge the capacitors when power is shut off. When
the generator on/off switch is turned off, the normally closed contacts of
relays K1 and K2 close and each relay connects two 1.2K, 50-watt resistors in
series across each capacitor bank, discharging the capacitors to a safe volt-
age below 24 VDC within two minutes. When the generator on/off switch is
turned on, the relay contacts open, disconnecting the resistors from the
capacitor banks. A 0.1 uF capacitor in series with a 220 ohm resistor is con-
nected across the normally closed contacts of each relay to prevent arcing
whenever the relay contacts open.
In addition to the above, the Line Monitor circuit controls the turn-on in-rush
current of the system by shunting the 2 ohm resistors in series with the input
transformers of the system only after the +24V LVPS is energized. This per-
mits the transformers to slowly change before the contactor is energized, pre-
venting arcing of the contactor's contacts and over-current conditions on
turn-on.
Auto-Shutoff Circuit
The Auto-Shutoff Circuit turns off the system after one hour of non-usage via
a command from the Logic Circuit. The Operator Control Panel Circuit con-
tains a microprocessor that monitors the Operator Control Panel (OCP) for
any key activation. If no key is pressed on the OCP for a user-selectable
period (30-180 mins.), the microprocessor generated AUTO SHUTOFF signal
energizes Auto-Shutoff Relay K4. This opens a ground, deactivating System
On/Off Relay K4, which turns off the generator via Contactor K1. In order to
turn on the generator, the system ON/OFF switch on the OCP has to be set to
the OFF position. This turns off Auto-Shutoff Relay K4. When the system
ON/OFF switch (on the OCP) is set back to the ON position, a ground signal is
sent via Auto-Shutoff Relay K4 to System On/Off Relay K4, thus turning on
the generator.