Medrad ProVis Mark V, Руководство по обслуживанию

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Mark V ProVis Injection System
10 - 2
PDCI
Refer to Figures 10.1 and 10.2 for block diagrams of the PDCI.
Brake Circuit
Q1, Q2, Q3 The Brake Circuit is used to stop the plunger motor at the end of an
injection, or if an error condition occurs during the injection. This pro-
cess is called Dynamic Braking. When the Safe Relay opens, the
motor will continue to turn, thereby acting as a generator producing
voltage. When the brake is activated, the motor winding is connected
across two .75 ohm, 5 watt resistors, stopping the motor. At the end of
an injection, the error signal (ERRSIG, a command from the Servo
Control Card) goes negative (-1V), activating the Brake Sensing Cir-
cuit Q1 - Q3, thus stopping the motor. Zener diode D1 protects Q1 by
limiting gate to source voltage to 15 volts. A SYSTEM OVERRIDE,
AUX MONITOR, or overrate condition can also activate the brake.
Overcurrent
Shutdown
U1A, DRC Q1 The Overcurrent Shutdown Circuit opens the plunger motor voltage
path if excessive current is flowing through the motor circuit. Sampling
Resistor R4 (on DRCI) is in series with the motor, and voltage across
it is directly proportional to the current through the motor. This voltage
is an input to Motor Current Amplifier U1D, the output of which is
applied to the non-inverting input of Overcurrent Shutdown compara-
tor U1A. The inverting input to U1A is connected to a voltage divider,
establishing an Overcurrent Shutdown reference. When output of
U1D rises above reference voltage at U1A, the output of U1A
switches to negative saturation. This negative voltage is applied to the
gate of Overcurrent Shutdown FET Q1 on the DRCI, forcing it into cut-
off, and opening the motor voltage path.
Safe Relay /
Safe Relay Enable
K1, Q7 Safe Relay K1 completes the motor voltage path between the SCR
Bridge stage, and the Plunger Motor. K1 also provides an additional
pair of normally-closed contacts to allow the Mechanical Stop Motor to
run while the injector is disarmed, yet prevent the Plunger motor from
running. K1 is enabled by either a Forward or Reverse load command
from the injector head, or when the injector is armed (Safe Relay
Enable [SAFRELEN] from the SCC). In both cases, theses signals
cause Q5 to conduct, providing a ground path to energize K1
(SAFRELO). This action disables the Mechanical Stop Motor by
breaking connections to the motor, and allowing power to flow to the
Plunger motor. The Safe Relay is disabled by a SYSTEM OVERRIDE/
AUX MONITOR from the PDCI, or a loss of the SAFRELEN from the
SCC.
Single Button Disarm from Injector Head - When the injector is armed,
and the SAFRELEN in the active high state, Q12 conducts, shunting
R56. This process allows “Single Button” disarming of the injector
head. When the injector is armed, if any single button on the injector