Siemens MOBILETT Plus Manual page 23

Capacitor-bank charging circuit
In the final phase of the charging process for the capacitor bank the actual value of the
capacitor voltage "CAP VOL" on the CPU board D1 is monitored via a software-controlled
window discriminator.
When the actual value exceeds the threshold voltage of U
HIGH" is switched off and the green "ready" LED on the Control and display panel is
turned on, see Fig. 1.
The signal "CHARGE LOW" is then switched on. This regulates the actual value of the
capacitor voltage "CAP VOL", with a low charging current up to the desired final value.
Then "CAPVOL" will be held at, or slightly above, the reference value by switching off and
switching on "CHARGE LOW".
The "ready" lamp remains turned on as long as the actual value of the capacitor voltage
"CAP VOL" remains within the hysteresis tolerance range of ± 1.2 V, see Fig. 1.
If the capacitor voltage "CAP VOL" is not within the threshold voltage range of ± 1.2 V due
to, for instance an unusual large leakage current or another kV selection, the green
"ready" LED on the Control and display panel will be turned off.
The capacitor is then either charged with "CHARGE HIGH" or discharged with "DIS-
CHARGE" as required until the actual voltage value "CAP VOL" of the capacitor bank is
within the tolerance range of ± 0.8 V.
The green "ready" LED on the Control and display panel is then turned on again.
The unit is ready to operate!
U +1.2 V
c
U +0.8 V
c
U
ref
U -0.8 V
c
U -1.2 V
c
Fig. 1
Siemens-Elema AB
Solna, Sweden
Discharge with
"CHARGE LOW" or
"DISCHARGE"
"DISCHARGE" stop!
"Ready"
on
Charge with
"CHARGE HIGH"
Register 6 SPR8-215.850.02
Rev. 01
Hysteresis threshold
Charge with
"CHARGE LOW"
Page 3 of 6
01.02 SPS-UD
- 0.8V, the signal "CHARGE
c
After switching off
load charge with
"CHARGE HIGH"
Discharge e.g.
disturbance
MOBILETT Plus/ Plus E
7 - 3