Vacuumtight M Series High Power connector

Vacuumtight M Series

When a prototype is designed with a view to winning a competition, each element can make all the difference.

In April, EPFLoop did not have to think twice about where to find the best connector solution. The Swiss Federal Institute of Technology, Lausanne is only a stone’s throw away from LEMO’s global headquarters and the two institutions have been linked by many years of partnership.

The EPFLoop team needed a solution to connect the engine interface with the battery interface of their pod. The requirements were to carry high electric current (with a peak amperage of 600 amps) for about 15 seconds, not to heat by more than 30 degrees (to save battery power and to avoid damaging surrounding parts), withstand high acceleration and possible shock. Moreover, and obviously, it should perfectly function in the vacuum environment of SpaceX’s hyperloop tube.

By a fortunate coincidence, LEMO’s R&D were actually working on the development of the M Series High Power connector for motorsport applications (see CONNECTED 10). Powerful, lightweight, robust, all it needed was to be made vacuumtight to meet the students’ specifications.

Given the tight schedule, Alex Patenaude, the engineer in charge of the project, went for the most pragmatic solution: he started with simple O-rings. The size and contact arrangement were adapted to this solution, which was less complicated and cheaper than the usual vacuumtight technique of epoxy resin potting. After fitting an O-ring on the contact and two on the socket outer shell, the tests could start running. The socket was mounted on the test equipment — low pressure was generated, helium sprayed around the connector and the quantity of helium that passed through the connector was measured. Great surprise: the results (1.2 × 10-8 mbar.l.s-1) were fully in line with the LEMO standards for vacuumtight connectors. The engineer has taken an even further step by radially constraining the contact in its socket, in order to test such limit positions through new measurements. The socket stayed perfectly vacuumtight in spite of the constraints.

All that was left to do was to verify the heat-up of the connector. Alex Patenaude measured a modest 25-degree temperature rise at 400 amps, in ambient temperature or at 40°C.

Based on EPFLoop’s extrapolation, the increase in temperature would still be perfectly manageable at the required 600 amps. There seemed to be no risks at all from this point of view, all looked just perfect.

LEMO assembled 16 pairs of connectors and supplied them to EPFLoop in May 2018, a mere two months after their initial request. At the end of July in California, the new connector raced through the hyperloop tube without a glitch. Elon Musk’s competition was to be its testing campaign and EPFLoop its first user.

There will be other users: the vacuumtight option of the M Series High Power connectors will be available in several sizes and will be included in the LEMO product range. Few applications require a vacuumtight option — maybe some major research institutes with vacuumtight installations. However, vacuumtight also means waterproof and there are potentially quite a few applications which require high power AND weatherproof sockets: electric cars and scooters, vehicles, large drones… a bright future lies ahead of the M Series.