
Function
2 Function
2 1 Intended use
The AC/DC sensitive residual current monitor RCMA423 is designed for use in earthed systems (TN and TT
systems) where DC and AC fault currents may occur.
These are in particular loads containing six-pulse rectifiers or one way rectifiers with smoothing, such as
converters, battery chargers, construction site equipment with frequency-controlled drives. Two separately
adjustable response ranges allow to distinguish between prewarning (IΔn1 = 50…100 % of the set response
value IΔn2) and alarm (IΔn2). Since the values are measured with measuring current transformers, the RCMA423 is
nearly independent of the nominal voltage and the load current of the system being monitored.
In order to meet the requirements of the applicable standards, customised parameter settings must be made
on the equipment in order to adapt it to local equipment and operating conditions. Please heed the limits of
the range of application indicated in the technical data. Any use other than that described in this manual is
regarded as improper.
2 2 Device features
•AC/DC sensitive residual current monitor Type B according to IEC 62020 and IEC 60755
•Two separately adjustable response ranges (prewarning, alarm)
•Adjustable switching hysteresis
•R.m.s. value measurement
•Starting delay, response delay and delay on release
•Measured value display via multi-functional LC display
•Alarm indication via LEDs (AL1, AL2) and changeover contacts (K1, K2)
•N/C operation or N/O operation selectable
•Password protection against unauthorized parameter changing
•Fault memory function can be switched off
•CT connection monitoring
2 3 Function
Once the supply voltage US is applied, the starting delay is activated. Measured values changing during this
time do not influence the switching state of the alarm relays.
Die Differenzstrommessung erfolgt über einen externen Messstromwandler CTUB101- CTBC20…210(P)
The currently measured value is shown on the LC display. In this way any changes, for example when circuits
are connected to the system, can be recognized easily.
If the measured value exceeds one or both response values, the response delays ton1/2 start running. Once the
response delay ton1/2 has elapsed, the K1/ K2 alarm relays switch and the alarm LEDs AL1/AL2 light up.
If the residual current falls below the release value (response value minus hysteresis), the delay on release toff
begins. Once the release delay toff has elapsed, the alarm relays return to their original state and the alarm LEDs
AL1/AL2 go out. If the fault memory is activated, the alarm relays remain in the alarm state and the LEDs light
until the reset button is pressed or until the supply voltage is interrupted.
The device function can be tested using the test button. The parameterization of the device can be carried out
via the LC display and the function keys integrated in the front plate and can be password-protected.
8 RCMA423_D00063_04_M_XXEN/12.2023