The AC / DC sensitive residual current monitor RCMA475LY is designed for monitoring earthed power supply systems (TN and TT systems) where DC fault currents or residual currents continuously greater than zero 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.

The prewarning stage (50 % of the set response value I_Δn1) allow to distinguish between prewarning and alarm. Since the values are measured with measuring current transformers, the device is nearly independent of the load current and the nominal voltage of the system.

• Internal measuring current transformer ø 18 mm
• Two response values
  alarm IΔn1: 30 mA…500 mA (0…700 Hz)
  prewarning IΔn2: 50 % / 100 % of IΔn1
• Response delay, adjustable 0…10 s (prewarning 0 / 1 s)
• Two separate alarm relays with one changeover contact each
• N / O or N / C operation, selectable

• AC / DC sensitive residual current monitoring in earthed two, three or four conductor systems (TN and TT systems)
• AC / DC sensitive current monitoring of single conductors de-energised under normal conditions (e.g. N and PE conductors)
• Variable-speed drives
• Uninterruptible power supply systems (UPS)