Selwyn Corns outlines a new compact spring contact system with low contact resistance that can cope with large dimensional tolerances, offsets and angular deviations.

The electric power supply and distribution industry rely on a large amount of switchgear, including transformers, circuit breakers, isolator switches and feed-throughs. Many of these have detachable connectors which contain multiple contact elements to ensure good electrical contact. These elements have to be able to carry extremely high currents, particularly in the event of a short circuit.

This article was originally published in Smart Energy International issue 1-2020 and appeared in the PEI – Supplement. Read the full digimag here or subscribe to receive a print copy here.

They also need to provide the flexibility to compensate for mismatched dimensional tolerances in the two parts of the connector and guarantee a reliable connection even after a large number of mating cycles. For example, high and medium voltage installations are designed to have long maintenance intervals, with the first overhaul often not occurring until 25 years of operation, by which time up to 10,000 mating cycles may have occurred.

The MULTILAM flexo ML-CUX is a two-component spring contact system which optimises its electrical and mechanical properties, giving a high current carrying capacity and a low contact resistance, and producing minimal contact heating even with constant high loads and after thousands of mating cycles.

The high number of mating cycles possible is particularly advantageous in applications involving expansion joints, where thermal cycling can mean that the connector constantly needs to slide while remaining in full electrical contact.

Able to withstand extreme current peaks, it has a short-circuit current carrying capacity of up to 4.4 kA/cm. This means that fewer bands may be needed in larger configurations, allowing two or even three other contact elements to be replaced by a single ML-CUX. A more compact design and reduced material costs are therefore achievable without compromising performance.

A further advantage is its high tolerance compensation: the large contact area makes it highly flexible and able to cope with significant angular and axial offsets. This gives manufacturers more freedom to design a variety of contact solutions and allows simpler, more cost-effective production.

The MULTILAM contact system consists of a stainless steel spring carrier band with louvres attached by rivets. The carrier band is optimised for its mechanical properties, while the louvres’ design is chosen for their electrical properties. No compromises were made in the selection of the materials and the design of the contact louvre. This separation between the mechanical and electrical parts means a product that offers crucial advantages over coil spring contacts, while being able to be installed just as easily.

With a low contact resistance and minimal contact heating, even at constant high loads, its high current carrying capacity enables a significantly more compact design, allowing it to be implemented more easily even in smaller systems. This ultimately benefits users by leading to lower costs for material use.

Large working area

A simple shallow rectangular slot is all that is needed to hold the ML-CUX. This allows for slimmer designs than with using coil spring contacts while still guaranteeing reliable positioning between plug and socket. Installation is simple, as it only involves placement of the contact louvre in the slot by hand.

In the electricity supply and distribution industry, components of different origins are often installed together. Engineers are therefore faced with mechanical problems and have to deal with large dimensional tolerances, offsets and angular deviations.

It is possible to overcome these challenges as the large working area makes it highly flexible and able to compensate for significant angular and axial offsets without difficulty. This allows more freedom to design a wide variety of applications and enables simpler, cost-effective production.

ABOUT THE AUTHOR

Selwyn Corns is managing director of Stäubli Electrical Connectors UK.