Device description
15
RCMB300-series_D00372_01_M_XXEN/06.2019
3.4 Functional description
Residual current I
Δn
The residual current monitoring module measures both AC and DC currents. Tripping
takes place based on the determined r.m.s. value. When the response value set for I
Δn2
(alarm) is exceeded by a residual current, the output relay K2 switches an undervoltage
release (recommended) or a shunt release (N/O operation) within the required tripping
time and the LED lights up red.
The individual components of the residual current (AC component, DC component)
and the r.m.s. value can be evaluated separately with the RCMB module. In addition, it
is possible to set the main alarm and prewarning for the individual components and as-
sign them to the two relays. The response values for the different components should
be within the same measuring range.
If the fault memory behaviour of relay K1 or K2 is activated, the device must be reset by
pressing the "T" button.
The RCMB module automatically checks the measuring current transformer and the
function of the residual current measurement cyclically.
Offset calibration
When the device has been installed, an offset calibration should first be carried out (Re-
fer to "Offset calibration" on page 27.) After successful offset calibration, the multicol-
our LED lights up green and the device is ready for operation.
Test
Press the "T" button or the external test button for 5…10 s to start the manual self test
of the device.
Reset
Press the "T" button or the external test button for 1.5...5 s to reset the device.
RS-485 interface
The RS-485 interface enables both reading out the measured values and setting the pa-
rameters of the device via Modbus RTU. Furthermore, a test or a reset can be triggered
via the bus.
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