The RCM470LY-21 is a Type A residual current monitor designed for earthed systems (TN and TT systems) to monitor AC and pulsating DC residual currents. The device performs non-invasive measurements via external measuring current transformers, largely unaffected by load current and system voltage. When an earth fault is detected, the device triggers an alarm without disconnecting the power supply, providing advanced warning of developing ground faults.
Technical Specifications
· Order No.: B 9401 2021
· Response range: 10 mA…10 A
· Rated frequency: 40…400 Hz
· Response delay: 0…10 s (adjustable)
· Supply voltage: DC 9.6…84 V
· Measuring current transformers: W…, WR…, WS… series
· Display: LED bar graph (0…100%)
· Alarm output: 1 DPDT changeover contact, AC 250 V / 5 A
· Operating principle: Selectable normally energized or normally de-energized
· Fault memory: Selectable latching/non-latching mode
· Test/Reset: Built‑in TEST/RESET button; supports external push‑buttons
· Transformer connection monitoring: Continuously monitors external current transformer connection status
· Operating temperature: –10 °C … +55 °C
· Storage temperature: –40 °C … +70 °C
· Protection class: Housing IP30, terminals IP20
· Mounting: 35 mm DIN rail
· Weight: ≤ 350 g
· Standards compliance: IEC 62020, IEC 60755 (Type A)
Key Features
· Type A residual current monitoring: Detects sinusoidal AC and pulsating DC earth fault currents
· External measuring current transformer: Via W…, WR…, WS… series; measurement largely unaffected by load current and system voltage
· Wide adjustable response range: 10 mA…10 A steplessly adjustable
· Adjustable response delay: 0…10 s to prevent nuisance tripping
· LED bar graph: Real‑time display of measured value as percentage of set value (0…100%)
· Selectable fault memory: Latching (manual reset) or non‑latching (auto reset) mode
· Self‑test and reset: Built‑in TEST/RESET button; supports external push‑buttons for remote operation
· Transformer connection monitoring: Alarms immediately on wire break
· Sealable transparent cover: Prevents unauthorised parameter changes
Typical Applications
· Residual current monitoring in earthed systems (TN/TT systems)
· Motor and motor control systems
· Portable and stationary generators
· Alarm systems, safety devices
· Cooling equipment (e.g., refrigerators storing valuable frozen goods)
· Socket outlet circuits for permanently unattended equipment (air conditioning, EDP systems)
· Industrial control and heat tracing systems
· Busbar systems
· Off‑line single‑conductor current monitoring (PE conductor, N‑PE connection, etc.)
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