New Contactor Concept for Global Use in Railway Applications
Schaltbau is bringing out a completely new railway contactor as part of its CT1000 model series. Realising the demanding requirement profile in a solution that would be convincing overall, was the primary development objective. Particular attention was paid to controlling the arc. In this respect, the concept of the CT1000 applies a completely new, unique principle: for the first time, the advantages of electromagnetic and permanent magnetic blowing for arc guidance are combined in one system. The result is an economically and technically efficient, reliable system that can be used almost without limitation in global railway networks. The initial experience gained from a number of field tests is positive.
It is impossible to tackle the changing current directions of AC or two-direction DC switching requirements with purely permanent magnetic blowout, although the principle has a number of attractive advantages. It is cost-effective, compact, permanently available and offers a high degree of intensity in all situations because of the use of rare-earth magnets.
Electromagnetic blowout, on the other hand, is independent of the direction of the current. However, the dwindling effect in the critical power area (high operating voltages, low currents) has caused problems so far, as has the activation of the blowout coils. Economic and design factors have meant that they have only been dimensioned as a function of the extremely short duration of the existence of the arc (approx. 3-5 hundredths of a second) at the moment of disconnection.
Efficient extinguishing of the arc
The combination of permanent magnetic and electromagnetic blowout into one complete system produces a number of crucial advantages. In contrast to purely electromagnetic blowout concepts, the arcs between the opening contact pieces are ignited in strong magnetic fields (permanently magnetic). This means that the arc has an extremely short dwell time in the contact zones and minimises burn-up of the contacts. In addition, the strong magnetic fields support arc extinguishing in the critical current range.
The permanently magnetic driven arcs act like switches and activate the electromagnetic blowout coils. This is done without wear, so there is no need for additional parts susceptible to faults, thus guaranteeing maximum reliability. The combined effect of two blowout coils then drives the arc, independently of the direction of current, into the ceramic extinguishing area, where it is effectively extinguished through further expansion and cooling. Special guide structures reduce the plasma emission to a minimum.
The concept allows a simple design with comparatively few components, which are also not sensitive. The double-interrupting contact bridge means that there is no need for flexible wires for power transfer. The auxiliary contact option offers two powerful switching elements, and also has two diagnosis contacts, which clearly display the contactor states “open” and “closed”. A compact, visually attractive design rounds off the new appliance concept.
The materials that are used in the CT1000 model series comply with RoHS requirements and meet the international fire protection requirements. These single-pole make-contactors can also be switched together into two- or three-pole versions.
With the CT1000 range of products, Schaltbau is successfully implementing its decades of experience in the area of industrial and railway contactors.