Datasheet

40 TDB404006en / Main catalogue part 4 – Residual current monitors, Residual current monitoring systems / 07.2010
Dipl.-Ing. W. Bender GmbH & Co. KG • Londorfer Str. 65 • 35305 Grünberg • Phone: [phone] • Fax: [phone]
Subject to change ! – © Dipl.-Ing. W. Bender GmbH & Co. KG, Germany
4.2
Residual current monitor
RCMA420
AC/DC sensitive residual current monitor
for TN and TT systems
(AC, DC and pulsed DC currents)
RCMA420
Device features
• AC / DC sensitive residual current monitor
Type B acc. to IEC 62020 and IEC/TR 60755
• r.m.s. value measurement (AC+DC)
• Two separately adjustable response
values 10…500 mA
• Frequency range 0…2000 Hz
• Start-up delay, response delay and delay
on release
• Digital measured value display via
LC display
• Measured value memory for
operating value
• CT connection monitoring
• Power On LED, LEDs: Alarm 1 / 2
• Internal/external test/reset button
• Two separate alarm relays
(one changeover contact each)
• N/O or N/C operation and fault memory
behaviour selectable
• Continuous self monitoring
• Multi-functional LC display
• Password protection for device settings
• Sealable transparent cover
• Two-module enclosure (36 mm)
• RoHS compliant
• Push-wire terminal
(two terminals per connection)
Approvals and certifications
Product description
The AC/DC sensitive residual current monitor RCMA420 is designed for monitoring earthed
power supply systems (TN and TT systems) where smooth 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. Currents in single conductors
can be monitored too.
The prewarning stage (50…100 % of the set response value I
Δn2
) 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.
Applications
• AC/DC sensitive residual current monitoring in earthed two, three or four conductor systems
(TN and TT systems)
• Monitoring of variable-speed drives, UPS systems, construction site equipment, printing
machines, battery systems, laboratory equipment, wood working machines, MF welding
systems, furniture industry, medical electrical equipment, etc.
• AC/DC sensitive current monitoring of single conductors de-energised under normal
conditions (e.g. N and PE conductors)
Function
Once the supply voltage U
S
is applied, the start-up delay is activated. Measured values
changing during this time do not influence the switching state of the alarm relays.
Residual current measurement takes place via an external measuring current transformer
of the W20AB…W60AB series. 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
recognised easily. If the measured value exceeds the set response values, the response
delays t
on1 / 2
begin. Once the response delay t
on1 / 2
has elapsed, the K1/K2 alarm relays
switch and the alarm LEDs AL1/AL2 light up. If the current falls below the release value
(response value plus hysteresis), the release delay t
off
. When toff has elapsed, the alarm
relays return to their initial position 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. Parameters are assigned to the device via the LCD and the
control buttons on the front panel; this function can be password-protected.
Connection monitoring
The function of the device and the CT connections are continuously monitored. In the event
of a fault, the alarm relays K1 / K2 switch without delay, the alarm LEDs AL1 / AL2 / ON flash.
On removal of the fault, the alarm relays return to their initial position either automatically
or by pressing the reset button.