The RCMA474 is a Type B full current sensitive residual current monitor designed for earthed systems (TN and TT systems). It measures residual current non‑invasively via an external measuring current transformer. When an earth fault is detected, the device triggers an alarm without disconnecting the power supply, providing advanced warning of developing ground faults and effectively preventing nuisance tripping. The device complies with IEC 60755 and reliably detects smooth DC, pulsating DC and AC residual currents.
Technical Specifications
· Response range: AC/DC 30 mA … 3 A, 0 … 150 Hz
· Supply voltage: AC 230 V, 50/60 Hz
· Power consumption: 4.8 VA
· Relay contacts: AC 250 V / 5 A (two independent changeover contacts K1, K2)
· Display: Multi‑function LC display
· Protection class: Internal components IP30, terminals IP20
· Mounting: 35 mm DIN rail
· Software version: D209 V1.2
· Order number: B94042082
· Data sheet: 404003
Key Features
· Type B full current sensitivity – Detects smooth DC, pulsating DC and AC residual currents.
· Two independent alarm stages – Adjustable pre‑warning (IΔn1) and main alarm (IΔn2); response delay 0 … 10 s adjustable.
· External measuring current transformer – Non‑invasive measurement, largely unaffected by load current and system voltage.
· True RMS measurement (TRMS) – AC+DC true RMS measurement ensures high accuracy even in harmonic‑rich systems.
· Multi‑function LC display – Shows real‑time residual current and supports menu navigation.
· LED bar graph – Displays the measured value as a percentage of the set alarm value.
· Selectable fault memory – Latching (manual reset) or non‑latching (auto reset) mode.
· Self‑test and reset – Built‑in TEST/RESET combination button; supports external push‑buttons for remote operation.
· Transformer connection monitoring – LED flashes and relays switch immediately on wire break or system fault.
· Sealable transparent cover – Prevents unauthorised parameter changes.
Front Panel Indicator Description
· ON (green) – Power indicator. Steady ON during normal operation; flashes on system or CT fault.
· AL1 (yellow) – Pre‑warning indicator. Steady ON when residual current exceeds IΔn1; flashes on fault.
· AL2 (yellow) – Main alarm indicator. Steady ON when residual current exceeds IΔn2; flashes on fault.
· LED bar graph – Shows the current residual current as a percentage (0‑100%) of the set alarm value.
Typical Applications
· Residual current monitoring in earthed systems (TN/TT systems)
· Variable frequency drive systems, photovoltaic systems, EV charging stations
· Data centres, medical locations
· Permanently unattended equipment (air conditioning, EDP systems)
· Motor control systems, generators
· Cooling equipment, industrial control and heat tracing systems
· Welding equipment and industrial robots
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