Optimised current carrying capacity: Bridge to the electric future

The manufacturing industry is faced with the challenge of adapting its systems to increasing performance requirements – without claiming more space. Find out here how we at HARTING are improving the efficiency and performance of electrical connections through targeted design optimisations and advanced, leading-edge technologies.

The All Electric Society requires electrical energy, which is supplied by way of the power core both between and within the sectors. In many cases, the transition to electrified systems will entail higher performance levels or new systems with more power will have to be created.

The gains in on-board power in automobiles is an illustrative example from everyday life. This measure simplifies the implementation of so-called "break by wire" and "steer by wire" applications. The former refers to an electric braking system in which the braking forces are transmitted electronically and not mechanically, in other words by way of brake lines. The second refers to an electronic steering system in which the connection between the steering wheel and the wheels is also not mechanical, as with steering rods, but is executed via electrical signals. These performance gains also optimise the charging process for electric cars. Here, large amounts of energy have to be transferred to the vehicle by way of a connector in a short time so that the electric car is as powerful as a combustion engine when "refuelling". Similar examples can also be found in other sectors.

Despite the higher energy requirements, the available space remains unchanged. At the same time, the efficient installation, maintenance or operation calls for the use of connector, which must therefore be able to offer higher current-carrying capacity while retaining the same size.

This is where current carrying capacity enters the picture. It indicates the maximum current that a connector can transmit for a specific cable diameter. This capacity results from the balance between the heat generated due to the electrical resistance and the heat dissipated. The latter is dissipated both by radiation and by way of the cable. While higher current-carrying capacities can be realised more easily with larger connectors and cables, this is not an option in many applications. In some cases, active cooling of the connectors or the use of alternative plastic materials that allow higher temperatures will provide a solution.

Reducing electrical resistance is another alternative, which prevents heat from developing. This also improves energy efficiency. Ultimately, there are three key starting points for improving current carrying capacity: the connection of the cable, the contact material and the contact point itself.

There are various solutions for the cable connection. So-called "crimping", i.e. making a mechanical connection that provides both electrical contact and mechanical strength is a common technique in the energy sector.

A well-executed crimp considerably reduces the contact resistance due to the plastic deformation of the cable and the contact area. The right crimping tool and the correct parameters are crucial factors here. In terms of the contact material, the alloy selected is also of particular interest, as it can significantly increase conductivity. Copper alloy is generally used as the base material.

The resistance in the mating area is influenced by various factors. The number and size of the contact points can be optimised by the specific design: The larger the contact surface, the lower the resistance. The normal force – in other words, the force with which the mating parts are pressed together – also plays a major role in this context. A higher normal force increases the effective contact surface, meaning that more current can flow per contact point, whereby the choice of surface supports this effect. A higher normal force also entails greater insertion force, however, which in turn can increase wear.

Ultimately, it is evident that the optimised design of many parameters improves the overall current carrying capacity. State of the art simulation tools enable us to optimise the current carrying capacity as early as the design phase, meaning that different designs and materials can be selected and adapted accordingly.