Requirements met - Selectivity modules certified to NEC Class 2

SITOP select with NEC Class 2

The new modules certified to NEC Class 2 for the electronic monitoring of 24-volt control circuits limit the power per output to 100 volt amperes. Four control circuits with an adjustable output current range of 0.5 to 3 amperes can be implemented per selectivity module. Indeed, 24-volt infeed is possible using any 1, 2 or 3-phase Sitop power supply. One Sitop PSE200U selectivity module monitors up to four 24-volt load circuits for overload and short circuits. Irrespective of the cable lengths and cross-sections, the modules are also able to detect minimal overloads and “creeping” short circuits, and to isolate any output with a faulty path. This allows all other load circuits unaffected by the fault to continue being safely supplied with power. Variants with a common signaling contact and with single-channel signaling are available for remote diagnostics.

Benefits for customers

The NEC classification offers a whole range of benefits for customers. On the one hand, the wiring complexity and the costs for the acceptance are reduced by a control circuit according to NEC Class 2. On the other hand,in conjunction with the NEC Class 2 certified selectivity modules, one high-performance 24-volt power supply can now replace a large number of small NEC Class 2 power supply units. This cuts down on the space required and minimizes the amount of work involved in installation. The continuous status signal from the load circuit also ensures the rapid detection of faults should a problem occur. Using only a single digital input, the status information delivered by the selectivity modules with single channel signaling can be simply integrated into the existing Simatic S7. Evaluation takes place using free-of-charge function block for Simatic S7-1500/1200/300/400 for Step 7 and the TIA Portal Engineering Framework. Consequently, this allows asimple integration into S7 diagnostics and into higher-level control as well as operating and monitoring systems.