UMC710D4_D00379_00_M_XXEN / 01.2020 13
MEDICS® UMC710D4-..HA
2.5.3 Monitoring the device functions
The control circuits are constructed in such a way that even if a particular fault will almost certain-
ly occur, it cannot cause the power supply at the output of the automatic changeover module to
fail. Examples: Failure of the control voltage, operation of a protective device, a short-circuit to ex-
posed-conductive part or an earth fault, and an open circuit.
In addition to this, the module continuously monitors:
• The control circuit that is required for the next changeover process (coil, control con-
tacts, connections)
• For alarm indicator and test combinations, and alarm indicator and operator panels, de-
vice failure monitoring can also be programmed via the BMS bus.
Thanks to the redundant hardware design of the changeover module, it is guaranteed to function
safely even if the microcontroller should fail..
2.5.4 Monitoring of the neutral conductor
The neutral conductor is also monitored. When monitoring the neutral conductor in normal
operation, generally small currents of at least 10 mA are assumed to flow continuously through
the neutral conductor. The connection of an additional load avoids the likelihood of completely
symmetrical load currents. If the current falls below 10 mA in the neutral conductor, an interrupti-
on is to be expected. In this case, changeover takes place and the corresponding messages are
triggered. The neutral conductor monitoring can be deactivated (see instruction leaflet PRC487).
2.5.5 Power supply
SUD487 provides the power supply for the PRC487 control device and the control voltage for the
switch disconnectors from line 2, (or from line 1 if line 2 fails). It also provides the power supply
for the AN 450 power supply unit. The AN450 power supply unit supplies power to a maximum of
2 MK2430 alarm indicator and test combinations. It also provides the power supply for the optio-
nal alarm indicator and operator panel manual/automatic TMX-HA.
2.6
System components
PRC487
Control device for changeover and monitoring modules
SUD487
Voltage relay
BMS-Bus
Bender Measuring Device Interface
AN450
Power supply unit
RK464, RK474
Relay module
TMX-HA
Alarm indicator and operator panel manual/automatic
W1-S35, W2-S70
Measuring current transformers
