External Current Sensors

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The external Residual Current Sensors are available in 500:1, 1000:1, 2000:1 and 10.000:1 ratio and are limited for the output voltage to max. 27 Vrms. High voltages in the case of loose or broken wires are thus avoided. The Current Sensor measures the residual ground fault current according to the Core Balance principle, in that all the current carrying conductors, including the Neutral wire, are fed through the sensor. Normal Core Balance Transformers are made from 2 possible metal groups, mu-metal or Silicon Iron and have an as low as possible winding count to make sure that a high amplification factor is maintained. Both metals have their drawbacks:
  • Both metal groups are not linear and have their largest error in the low current region.
  • Mu-metal is very sensitive to low temperatures. Below 0°C most mu-metals stop operating, just when ice deposition is a ground fault hazard.
  • The power conversion of Silicon-Iron is poor, so bigger cross-section cores are used. The lower the detection level, the bigger the cross-section has to be.
  • Mu-metal is sensitive to lock-up due to dc currents. Over a long time it may restore, but one never knows when and how good the core will perform when needed. A high ac current can restore the correct trip point, at the cost of a system trip.
Modern electronics, with some precautions, can overcome the standard problems with Silicon-Iron materials. The drawbacks of mu-metals are material related and cannot be handled by electronics and are most dangerous to use due to lock-up and low temperature behaviour.

Our state-of-the-art Ground Fault protection devices consisting of Silicon-Iron core material with a small cross-section area to save material and highly integrated electronics makes it possible to have an accurate trip current range of 30 mA to 60 A and a Short Circuit detection of over 160 A using one and the same Current Sensor.

Round windowed External Current Sensors

Round External Current Sensor
Round External Current Sensor dimensions drawing
Round External Current Sensor CB5-50
Dimensions in mm Current ratio
A B C D E F G H I 500 1000 2000 10.000
65 112 63 30 120 15 17 29 --- CS5−65 --- --- ---
90 125 75 30 136 15 17 29 --- CS5−90 --- --- ---
95 150 75 45 150 25 16 23 --- --- CS10−95 CS20−95 CS100−95
144 207 105 48 204 28 20 37 55 --- CS10−144 CS20−144 CS100−144
150 207 105 39 204 20 20 37 55 CS5−150 --- --- ---
240 305 150 40 305 17 20 37 55 CS5−240 CS10−240 CS20−240 CS100−240

Square windowed External Current Sensors

Square windowed External Current Sensor
Square windowed External Current Sensor dimensions drawing
Dimensions in mm Current ratio
A B C D E F G H I J K L 500 1000 2000 10.000
150 170 293 225 180 265 20 20 40 20 38 55 CS5−1517 --- --- ---
103 250 373 196 140 345 20 20 40 20 38 55 CS5−1025 CS10−1025 CS20−1025 ---
102 350 477 198 142 449 20 20 40 20 38 55 CS5−1035 CS10−1035 CS20−1035 ---

These sensors are available in both split and un-split versions.
In un-split versions dimensions E, F and G are not applicable.

Top Hat Current Sensor dimensions drawing
Dimensions in mm Current ratio
A B C D E F G H I J K L M 500 1000 2000 10.000
300 300 470 440 360 406 30 60 64 260 440 12 17 CS5−3030 --- --- ---
200 286 387 282 --- --- --- 40 --- 241 363,5 12 17 CS5−2028 CS10−2028 CS20−2028 CS100−2028

The CS5-3030 is available in both split and un-split versions.
In the un-split version dimensions E, F and G are not applicable.
For the CSxx-2028 split-core versions are not available

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