MOBILETT Plus/ Plus E Register 6 SPR8-215.850.02 Page 2 of 6 Siemens-Elema AB
Rev. 01 01.02 SPS-UD Solna, Sweden
7 - 2 Capacitor-bank charging circuit
When the unit is switched on and the self-test and the initialization phase are completed,
the charging process in the capacitor bank, M1, is initiated with the control signal
”CHARGE HIGH”.
This signal is fed to the control logic on board D7.
The control logic generates control pulses for the BUCK CONVERTER on board D7 with
the appropriate pulse-pause modulation data, which control the charging of the capacitor
bank, M1.
The entire charging process, if the initial capacitor voltage is <10 V, takes place in three
distinct phases.
If the initial voltage is >10 V, the phases 1 and 2 are omitted.
• Phase 1 charging the capacitor bank to a voltage of about 150 V.
• Phase 2 includes switching off the control signal ”CHARGE HIGH” and measuring and
monitoring the voltage value of 150 V reached over a time of about 5 s.
• Phase 3 includes switching on of the control signal ”CHARGE HIGH” and the
completion of the kV-dependent charging procedure.
After the charging process, a regulation process, is performed to maintain the final value
attain-ed.
The corresponding final values are:
300 V with a selected tube voltage of <45 kV
325 V with a selected tube voltage of 45 kV and <50 kV
350 V with a selected tube voltage of 50 kV
The drop in the capacitor voltage, which may take place during the 5 s pause in phase 2,
is a measure of the leakage current of the capacitor bank. If the drop is too large, the con-
trol signal "DISCHARGE" is switched on and an error message is shown on the display.
As long as the capacitor bank is being charged with ”CHARGE HIGH” the microprocessor
on board D1 can not switch on any other major power consuming device. However, the
operating personnel can still request this via a manual switch-on procedure.
In case this is done, such as switching on the collimator lamp or the turn plate, the micro-
processor on the CPU board D1 interrupts the charging procedure. ”CHARGE HIGH” is
then switched off for the duration of the new routine required.
When the high-power consuming device is switched off, the charging process will be con-
tinued with the signal ”CHARGE HIGH”.
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