MOBILETT Plus/ Plus E Register 6 SPR8-215.850.02 Page 4 of 6 Siemens-Elema AB
Rev. 01 01.02 SPS-UD Solna, Sweden
7 - 4 Capacitor-bank charging circuit
Charging circuit errors 7
When an error occurs in the charging circuit function or in the power capacitor the follow-
ing actions are initiated:
By the buzzer on board D3:
• 10 beep tones are generated
In addition the green
• ”ready” LED is turned off.
• the parameter display is switched off
The controlled discharge procedure for the capacitor bank is initiated with the
• ”DISCHARGE” signal, and an
• error message is shown in the parameter display.
The discharge procedure for the capacitor bank continues until the fault indicated is
switched off by pressing the selection button ”kV+” or by switching off the unit and then
switching it on again.
Along with the software-controlled monitoring system for the signal ”CAP VOL” on the
CPU board D1 there is also a hardware monitoring circuit on board D7.
This monitors the potential difference across the capacitor bank.
The potential difference between test points ”CAP POS” and ”CAP NEG” is fed via a dif-
ferential amplifier to a comparator. There the output voltage from the differential amplifier
is compared with a threshold voltage of 360V.
If the output voltage from the differential amplifier exceeds this threshold voltage, the sig-
nal ”OVERVOLTAGE” will be generated and the LED v12 on board D7 will be lit.
The signal ”OVERVOLTAGE” is fed to the CPU board D1, initiating the routines described
above for generating an error message and protecting the capacitor bank.
Other error messages are:
• Voltage rise in capacitor bank too fast,
• Voltage rise in capacitor bank too slow, or
• Leakage current in capacitor bank too large.
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