Brivo OEC 715/785/865/865 Mobile C-Arm X-Ray Product Service Manual
2-52
For the higher protect circuit point the value is set 120kV. When kV feedback signal KV- or kV+ is higher than
reference value in U10-2 and U11-2 the STOP signal is activated. At the same time led DS5 lightens. Jumper
W1 can disable this protect circuit. If jumper W1 is short circuit the higher protect circuit is disable.
For the over current protect circuit point the value is set 100A. when inverter output current measured by
current transformer is higher than the reference value in U17-2 the STOP signal is activated. At the same
time led DS56 lightens. Just like kV lower protect circuit this protect circuit is enable after a time of 6ms after
giving the exposure command.
For the DC bus error protect circuit point the value is set 250V and 360V. When DC bus voltage is lower than
250V or higher than 360V the exposure is disable. To the circuit, when DC bus voltage signal UDC is higher
than reference value in U19-1 and U19-2 the STOP signal is activated. At the same time led DS8 lightens.
Jumper W1 can disable this protect circuit. If jumper W1 is short circuit the higher protect circuit is disable.
For the kV unbalance protect circuit point the value is set 10kV. When difference between +kV absolute
value and –kV absolute value in the monoblock is higher than 10kV the exposure is disable. To the circuit
when difference signal KVN is higher than the reference value in U18-2 the STOP signal is activated. At the
same time led DS57 lightens.
For the IGBT error protect, the driver IC U23, U24, U26, U27 can provide this functional circuit. When IGBT is
short circuit those 4 IC will send out fault signal to disable exposure.
All the protect threshold is as follows.
kV higher protect circuit
Over current protect circuit
IGBT error protect circuit
DC bus error protect circuit
DC voltage<250V, or DC voltage>360V
kV unbalance protect circuit
LED OUTPUT
KV control board provides LED output warning when protect circuit is activated. All warning state can be
clear through pushing switch S1 or energizing the kV control board again.
The IGBT board in the generator includes fuse F, IGBT Q1,Q2,Q3,Q4, snubber circuit (composed by R,C,D
components) and common inductor L. The drive signal for IGBT is given by the kV control board. The IGBT
board actually is a DC-AC inverter and the DC input of this board is the output of a AC-DC converter
consisted by the main transformer, rectifier bridge and the DC bus capacitor. For the serial resonant
frequency of resonant circuit is nearly 40kHz, the IGBT board provides 40KHz variable AC power to
Monoblock.
The Block diagram of the IGBT board is shown as follows:
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