benderResidual current monitor RCMA475LY

Product description

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 IΔn1) 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.

Application

• AC / DC sensitive residual current monitoring in earthed two, three or four conductor 

systems.

• AC / DC sensitive current monitoring of single conductors de-energized under normal 

conditions (e. g. N and PE conductors).

• Variable-speed drives

• Uninterruptible power supply systems (UPS)

Device features

• 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

• Adjustable response delay 0…10 s 

(prewarning 0 / 1 s) 

• Two separately adjustable alarm relays 

with one changeover contact each

• N / O or N / C operation 

• Fault memory 

• Combined TEST and RESET button

• Connection external TEST and RESET 

button

• LED bar graph indicator IΔn 0…100 % 

• Connection external measuring instrument IΔn 0…100 % 

• Sealable transparent cover

• Separate supply voltage

• Type B acc. to IEC 60755

Function

Residual current monitoring takes place via an internal measuring current transformer. When 

the current respectively the residual current exceeds the set response value, the alarm LED 

lights and the associated alarm relay switches when the set response delay has elapsed. 

The alarm messages are stored. The fault memory can be reset by pressing the RESET button. 

The device function can be tested using the TEST button. 

The currently measured value in per cent related to the set response value is indicated on 

the LED bar graph indicator.

Wiring diagram – system connection, external connections

1 - Supply voltage US (see ordering information), a 6 A fuse recommended for line protection

2 - External measuring instrument

3 - External TEST and RESET button

4 - Alarm relay (alarm): switches when the fault current exceeds 

the response value IΔn1.

5 - Alarm relay (prewarning): switches when the fault current 

exceeds 50 % or 100 % of the response value IΔn1.

6 - Internal measuring current transformer

Do not route the PE conductor through the measuring current 

transformer !

1 - Supply voltage US (see ordering information), a 6 A fuse recommended for line protection

2 - External measuring instrument

3 - External TEST and RESET button

4 - Alarm relay (alarm): switches when the fault current exceeds 

the response value IΔn1.

5 - Alarm relay (prewarning): switches when the fault current 

exceeds 50 % or 100 % of the response value IΔn1.

6 - Internal measuring current transformer

Do not route the PE conductor through the measuring current 

transformer !

1 - Combined TEST and RESET button: short-time pressing (< 1 s) 

= RESET, long-time pressing (> 2 s) = TEST.

2 - Power On LED: lights when the device is in operation and flashes 

when the measuring range is exceeded.

3 - Alarm LED: lights when the fault current exceeds the set response value and flashes when 50 % of the set response value 

are reached.

4 - LED bar graph indicator, shows the measuring value in per 

cent related to the preset response value.

5 - Potentiometer for setting the response delay (0…1 s)

6 - Potentiometer for setting the response value (x 1…10 mA)

Setting of the DIP switches (white = switch position)

 7 - Contact 21-22-24 (prewarning)

A - at 50 % of IΔn1

B - at 100 % of IΔn1

 8 - Response delay prewarning

A - Delay 1 s

B - Delay 0 s

 9 - Alarm relay

A - N / O operation

B - N / C operation

 10 - Response range

A - 30 mA x 1…10 B - 50 mA

 11 - Response delay

A - Setting value t

/s x10

B - Setting value t

/s x1

Technical data residual current monitor RCMA475LY

Insulation coordination acc. to IEC 60664-1

Rated insulation voltage AC 250 V

Rated impulse voltage / pollution degree 4 kV / 3

Voltage ranges

Supply voltage US see ordering information

Operating range of US 0.85…1.1 x US

Frequency range of US DC / 50…60 Hz

Power consumption ≤ 3.5 VA

Measuring circuit/response values

Internal measuring current transformer ø 18 mm

Operating characteristic acc. to IEC 60755 Type B

Rated residual operating current IΔn2 (prewarning) 50 / 100 % of IΔn1

Response delay tv 0 / 1 s

Rated residual operating current IΔn1 (alarm) 30…500 mA

Response delay tv, adjustable 0…10 s

Rated frequency 0…700 Hz

Relative percentage error 0…- 25 %

Hysteresis approx. 25 % of the response value

Response time tan at IΔn1 = 1 x IΔn1 / 2 (tv = 0 s) < 70 ms

Response time tan at IΔn1 = 5 x IΔn1 / 2 (tv = 0 s) < 40 ms

Displays

LED bar graph indicator 0…100 %