
Function
2 Function
2 1 Intended use
The AC/DC sensitive residual current monitor RCMA420 is designed for use in earthed s stems (TN and TT
s stems) where DC and AC fault currents ma occur.
These are in particular loads containing six-pulse rectifiers or one wa rectifiers with smoothing, such as
converters, batter chargers, construction site equipment with frequenc -controlled drives. Two separatel
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 RCMA is
nearl independent of the nominal voltage and the load current of the s stem 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. An use other than that described in this manual is
regarded as improper.
2 2 Device features
•AC/DC sensitive residual current monitor T pe B according to IEC 62020 and IEC 60755
•Two separatel adjustable response ranges (prewarning, alarm)
•Adjustable switching h steresis
•R.m.s. value measurement
•Starting dela , response dela and dela on release
•Measured value displa via multi-functional LC displa
•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 memor function can be switched off
•CT connection monitoring
2 3 Function
Once the suppl voltage US is applied, the starting dela is activated. Measured values changing during this
time do not influence the switching state of the alarm rela s.
Residual current measurement takes place via an external measuring current transformer CTUB101- CTBC20…
60.
The currentl measured value is shown on the LC displa . In this wa an changes, for example when circuits
are connected to the s stem, can be recognized easil .
If the measured value exceeds one or both response values, the response dela s ton1/2 start running. Once the
response dela ton1/2 has elapsed, the K1/ K2 alarm rela s switch and the alarm LEDs AL1/AL2 light up.
If the residual current falls below the release value (response value minus h steresis), the dela on release toff
begins. Once the release dela toff has elapsed, the alarm rela s return to their original state and the alarm LEDs
AL1/AL2 go out. If the fault memor is activated, the alarm rela s remain in the alarm state and the LEDs light
until the reset button is pressed or until the suppl 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 displa and the function ke s integrated in the front plate and can be password-protected.
8 RCMA420_D00059_05_M_XXEN/12.2023