Beckhoff SCT6 Series Manual page 13

Product overview
Fig. 5: Characteristics fluxgate current measurement technology
The detection winding now measures the induced current of the excitation winding (blue). If the measuring
current I is 0, then 0 A is also measured, since no compensating current is generated for compensation.
prim
If the measuring current I is not equal to 0, a compensating current is generated through both cores, which
prim
again compensates for the disproportion of the magnetic flux density B in core 1 and core 2. Due to the
compensation, I is 0 again.
sense
The measured compensating current provides information about the current to be measured I .
prim
Together with a fixed excitation frequency, this leads to improved accuracy and stability.
General description of the fluxgate current measurement technology
The SCT series SCT5xxx is used for monitoring differential currents in electrical power supply systems that
do not require fast system shutdown. The SCT5xxx type B/B+ can measure DC and AC residual currents at
frequencies up to 100 kHz.
This makes this differential current transformer compatible with a wide range of industrial applications, loads
and power sources. With its user-selectable settings, this series provides a flexible platform for differential
current measurement suitable for any possible application, both at the time of industrial plant design and
when expanding with new modern loads operating at DC voltages or high switching frequencies that
increase the amount of leakage current in the system.
The SCT5xxx have an analog 4 - 20 mA output, which represents the real-time RMS value (TRMS) of the
measured residual current for connection to a PLC, for example. In addition, a potential-free relay output
(NO / NC) with a freely selectable residual current limit can be used for warning or even system shutdown if
the TRMS residual current measured value has exceeded the preset value. The status of the relay output is
replicated on an LED for visual indication on the device itself. A built-in test button and an external test
button input are provided for periodic testing of the SCT5xxx according to the applicable product standards.
Only a single 24 Vdc power supply should be provided for the SCT5xxx.
SCT6xxx Version: 1.3 13