With the ring current transformer SCT5564, Beckhoff offers a universal current-sensitive measurement system for AC and DC residual currents in accordance with EN/IEC 62020-1. Its use in machine monitoring ensures, among other things, higher system availability and minimization of maintenance costs thanks to early detection of insulation faults.
The SCT5564 residual current transformer (type B/B+) can be used as a residual current monitor (RCM) and can measure DC and AC residual currents with a frequency of up to 100 kHz in the range of 0 to 2 A. With its numerous setting options, this RCM offers a flexible platform for differential current measurement and is suitable for a wide range of system engineering applications. This offers advantages both in the planning phase of an industrial plant and when expanding to include new loads operating at DC voltages or high switching frequencies, which can potentially increase the leakage current in the overall system. In addition, early detection of insulation faults enables predictive maintenance, which increases system availability. Unwanted trips of the RCD due to decreased insulation of the machine are also avoided, and the expense of (repeated) insulation tests according to DGUV v3/VDE 0100 is replaced by an effective and permanent residual current measurement.
The SCT5564 differential current transformer has a 4…20 mA analog output that represents the real-time root mean square value (TRMS) of the measured differential current. In addition, a potential-free (NO/NC) relay output with freely selectable residual current can be used for warning purposes or even for system shutdown if the measured TRMS residual current value exceeds the preset value. A test button and external test button input are provided for periodic testing of the RCM in accordance with applicable product standards.
Crucial advantages and added value with PC-based control technology
Fault currents can also occur during normal operation, for example due to magnetization of an electric motor during starting. In these cases, the perfect integration of the current transformer in Beckhoff’s PC-based control technology creates special application advantages. In the mentioned example, the information available in the control system about the starting of a motor can reliably exclude false activations. This is especially relevant when multiple motors or actuators are used in a machine, as an increasing residual current and thus a probable insulation fault can be directly assigned to the component in question without having to measure the differential current of each individual drive. The same is true, for example, of the monitoring of heating elements in plastics machines, where loss of insulation due to aging can be effectively and cost-effectively prevented by early replacement, through a single central metering device and with the corresponding control data.
